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SeqFan

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Welcome to the SeqFan Google Group, a mailing list for Integer SEQuence FANs!

Appropriate topics for discussion are all aspects of integer sequences, especially those related to the On-Line Encyclopedia of Integer Sequences (the OEIS). The mailing list will also carry announcements from time to time related to maintaining the OEIS.

Etiquette for the SeqFan Mailing List:
- Please be polite and courteous.
- Make sure your message is accurate and complete; read it before posting it. It is going to 260+ people.
- Stay on topic, stick to facts, topics should be limited to sequences and mathematics.
- Do not post too often. Take time to collect all your thoughts into one reply.
- We have the capability of moderating posts from individual users, but we would rather not have to invoke it.
- Messages should be in English. But remember many members are not native speakers of English.
- If you have a question about a particular OEIS entry, consider contacting the author through the "Email this user" feature in the OEIS Wiki.
- Do not express opinions about which sequences are appropriate for the OEIS (leave that to the EiC's)

The archives of this Google Group are viewable by anyone on the web.

0 selected

Max Alekseyev, … Allan Wechsler8

3:23 PM

a new solution to Subbarao's congruence (Guy's UPINT problem B37)

Hi Robert, Yes, the next step would be to create a sequence of such composite solutions 4, ... I'

unread,

a new solution to Subbarao's congruence (Guy's UPINT problem B37)

Hi Robert, Yes, the next step would be to create a sequence of such composite solutions 4, ... I'

3:23 PM

Natalia L. Skirrow, Neil Sloane2

9:57 AM

requesting scan of p. 228 from Symmetric Function and Allied Tables (1966)

Here you go! Can you upload it yourself to the sequence? Best regards Neil Neil JA Sloane, Chairman,

unread,

requesting scan of p. 228 from Symmetric Function and Allied Tables (1966)

Here you go! Can you upload it yourself to the sequence? Best regards Neil Neil JA Sloane, Chairman,

9:57 AM

3:26 AM

A274967 and A121707

A274967 Odd composite numbers n which are not m-gonal number for 3 <= m < n. 4 77, 119, 143,

unread,

A274967 and A121707

A274967 Odd composite numbers n which are not m-gonal number for 3 <= m < n. 4 77, 119, 143,

3:26 AM

Alex Violette, … David Cleaver6

Oct 13

The Grid Arithmetic Problem

I wrote a python program to generate grids for the up/down/left/right (udlr) version of this Grid

unread,

The Grid Arithmetic Problem

I wrote a python program to generate grids for the up/down/left/right (udlr) version of this Grid

Oct 13

Elijah Beregovsky, … Victor Miller33

Oct 13

Edges needed to be removed to make graph bipartite

I'd like to put in a plug for MaxSat solvers. I used the MaxSat solver RC2 (using its interface

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Edges needed to be removed to make graph bipartite

I'd like to put in a plug for MaxSat solvers. I used the MaxSat solver RC2 (using its interface

Oct 13

Tom Duff, … Kevin Ryde6

Oct 12

Re: [SeqFan] should it be registered

Daniel Mondot <dmo...@gmail.com> writes: > > So, A078371 is related to every other

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Re: [SeqFan] should it be registered

Daniel Mondot <dmo...@gmail.com> writes: > > So, A078371 is related to every other

Oct 12

Oct 12

Hello everyone. I am not a mathematician. I didn't even go to school enough to do mathematics.

unread,

Hello everyone. I am not a mathematician. I didn't even go to school enough to do mathematics.

Oct 12

Oct 8

A273315 and a316572 and Wilson theorem

Hi to all, dearest fans what do you think about this... i noticed that A273315 and a316572 are

unread,

A273315 and a316572 and Wilson theorem

Hi to all, dearest fans what do you think about this... i noticed that A273315 and a316572 are

Oct 8

Sean A. Irvine, … Gareth McCaughan8

Oct 7

On 07/10/2025 10:51, Natalia L. Skirrow wrote: > I appreciate that I shouldn't expect support/

unread,

On 07/10/2025 10:51, Natalia L. Skirrow wrote: > I appreciate that I shouldn't expect support/

Oct 7

Oct 6

highly abundant numbers

In case anyone missed it, there was a fun MathOverflow question over the last week: https://

unread,

highly abundant numbers

In case anyone missed it, there was a fun MathOverflow question over the last week: https://

Oct 6

Davide Rotondo, … Arthur O'Dwyer7

Oct 6

I need your help, numbers that are built as follows... 2², 2³+3³, 2⁴+3⁴, 2⁵+3⁵+5⁵, 2⁶+3⁶+5⁶,...

On Mon, Oct 6, 2025 at 7:44 AM Daniel Mondot <dmo...@gmail.com> wrote: Keep in mind that GPT

unread,

I need your help, numbers that are built as follows... 2², 2³+3³, 2⁴+3⁴, 2⁵+3⁵+5⁵, 2⁶+3⁶+5⁶,...

On Mon, Oct 6, 2025 at 7:44 AM Daniel Mondot <dmo...@gmail.com> wrote: Keep in mind that GPT

Oct 6

Konstantin Knop, … D. S. McNeil9

Oct 5

A309370 comments

Unfortunately they're only one-sided bounds, or I would. :-) I'll toss in a comment, though,

unread,

A309370 comments

Unfortunately they're only one-sided bounds, or I would. :-) I'll toss in a comment, though,

Oct 5

Oct 4

building an open-source knowledge graph system about the OEIS

I've recently begun building an independent open-source knowledge graph system about the OEIS. If

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building an open-source knowledge graph system about the OEIS

I've recently begun building an independent open-source knowledge graph system about the OEIS. If

Oct 4

Ali Sada, … Daniel Mondot12

Oct 3

Prime chains formed by repeatedly doubling a contiguous substring of digits

Hi Daniel and Charles, Looking at Cf's of A386395, I found that the two versions are perfectly

unread,

Prime chains formed by repeatedly doubling a contiguous substring of digits

Hi Daniel and Charles, Looking at Cf's of A386395, I found that the two versions are perfectly

Oct 3

Davide Rotondo, … Robert Israel9

Oct 3

A356742 Numbers k such that k and k+2 both have exactly 4 divisors.

To understand A356742: "divisors" means integer divisors, not prime divisors. $123$ has

unread,

A356742 Numbers k such that k and k+2 both have exactly 4 divisors.

To understand A356742: "divisors" means integer divisors, not prime divisors. $123$ has

Oct 3

Davide Rotondo, D. S. McNeil4

Oct 3

Primes not expressible as the sum of two triangular numbers.

Thank you very much Doug! See you soon Davide Il giorno ven 3 ott 2025 alle 1:28 PM DS McNeil <

unread,

Primes not expressible as the sum of two triangular numbers.

Thank you very much Doug! See you soon Davide Il giorno ven 3 ott 2025 alle 1:28 PM DS McNeil <

Oct 3

Christian Lawson-Perfect, … Arthur O'Dwyer3

Oct 2

A sequence to do with shuffling cards

Your sequence Axxx goes: 1, 1, 4, 10, 56, 304, 1956, 14856, 130008, 1237440, 13084540, 151656128, ...

unread,

A sequence to do with shuffling cards

Your sequence Axxx goes: 1, 1, 4, 10, 56, 304, 1956, 14856, 130008, 1237440, 13084540, 151656128, ...

Oct 2

Sean A. Irvine, D. S. McNeil2

Oct 1

Theta series for modular lattices

Disclaimer: this is right at the limit of "can kind of manage, but only with a tutorial open

unread,

Theta series for modular lattices

Disclaimer: this is right at the limit of "can kind of manage, but only with a tutorial open

Oct 1

Kelvin Voskuijl, … Sean A. Irvine5

Oct 1

Video about different kind of polygonal root of 2

Kelvin also already recently added: https://oeis.org/A388148 Decimal expansion of the tetrahedral

unread,

Video about different kind of polygonal root of 2

Kelvin also already recently added: https://oeis.org/A388148 Decimal expansion of the tetrahedral

Oct 1

Daniel Mondot, … Sean A. Irvine4

Sep 29

A000057, A064414 and more.

> General questions: > Would it be worth having 5 new sequences: > 1) The composite numbers

unread,

A000057, A064414 and more.

> General questions: > Would it be worth having 5 new sequences: > 1) The composite numbers

Sep 29

Tomasz Ordowski2

Sep 29

Covering sets for K2^n+4^n+1 with odd K

PS. Correction, it should be: [...] If (K+2^n)2^n+1 has a covering set, [...]. Sorry for my mistake

unread,

Covering sets for K2^n+4^n+1 with odd K

PS. Correction, it should be: [...] If (K+2^n)2^n+1 has a covering set, [...]. Sorry for my mistake

Sep 29

Davide Rotondo2

Sep 29

Primality test for Twin Prime numbers.

Ps i forgot these are weak pseudoprimes to base 27. Il giorno lun 29 set 2025 alle ore 10:13 Davide

unread,

Primality test for Twin Prime numbers.

Ps i forgot these are weak pseudoprimes to base 27. Il giorno lun 29 set 2025 alle ore 10:13 Davide

Sep 29

Tomasz Ordowski, D. S. McNeil4

Sep 28

PS. Here's something better for those interested. Let a(n) be the smallest odd k indivisible by 3

unread,

PS. Here's something better for those interested. Let a(n) be the smallest odd k indivisible by 3

Sep 28

Davide Rotondo, Jack Brennen4

Sep 27

Conjecture concerning the primes for which 8 is a primitive root and the smallest k such that k*n is a Niven (or Harshad) number.

Sorry i Miss 1667 in my check. My apolgies Il giorno sab 27 set 2025 alle 4:44 PM 'Jack Brennen

unread,

Conjecture concerning the primes for which 8 is a primitive root and the smallest k such that k*n is a Niven (or Harshad) number.

Sorry i Miss 1667 in my check. My apolgies Il giorno sab 27 set 2025 alle 4:44 PM 'Jack Brennen

Sep 27

Davide Rotondo, M F Hasler4

Sep 27

a(n) = smallest k such that k*n is a Niven (or Harshad) number.

Sorry I don't understand. Davide Il giorno ven 26 set 2025 alle ore 14:28 MF Hasler <mhasler@

unread,

a(n) = smallest k such that k*n is a Niven (or Harshad) number.

Sorry I don't understand. Davide Il giorno ven 26 set 2025 alle ore 14:28 MF Hasler <mhasler@

Sep 27

Tom Duff, … Joshua Searle5

Sep 26

Harshad (Niven) numbers on Numberphile

Ah, thanks for that! It is quite hard with only one term to go off if you don't match the right

unread,

Harshad (Niven) numbers on Numberphile

Ah, thanks for that! It is quite hard with only one term to go off if you don't match the right

Sep 26

谢逸凡, … Brendan13

Sep 26

[SeqFan] A problem about distances on a tree

None on 15 vertices (9.3 hours). I won't run 16 vertices, but if someone wants to spend 4-7 days

unread,

[SeqFan] A problem about distances on a tree

None on 15 vertices (9.3 hours). I won't run 16 vertices, but if someone wants to spend 4-7 days

Sep 26

Thomas Scheuerle

Sep 26

An interesting representation of the Collatz problem

Hello, I hope this isn't too off-topic, as this post is just trying to highlight a topic that may

unread,

An interesting representation of the Collatz problem

Hello, I hope this isn't too off-topic, as this post is just trying to highlight a topic that may

Sep 26

Sep 25

Questions about A389140 and A389141

Hi everyone, Hope all is well. I submitted these two sequences and I have some questions. I would

unread,

Questions about A389140 and A389141

Hi everyone, Hope all is well. I submitted these two sequences and I have some questions. I would

Sep 25

Arnav T, Giovanni Resta3

Sep 25

Growth and trajectories in an additive digit map

Mam Giovanni, Thank you very much for carefully reviewing my draft and pointing out the mistake after

unread,

Growth and trajectories in an additive digit map

Mam Giovanni, Thank you very much for carefully reviewing my draft and pointing out the mistake after

Sep 25

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