Exception in sum((4*n+1)/factorial(n),n,1,oo)

[Georgi Guninski]

hi,

var('n')
sum((4*n+1)/factorial(n),n,1,oo)

TypeError: 'NoneType' object is not callable

[Eric Gourgoulhon]

I confirm the bug with Sage 10.3.beta7. It seems to be linked with the Maxima interface. 

Meanwhile, a workaround is to use the SymPy interface: 

sage: sum((4*n+1)/factorial(n), n, 1, oo, algorithm='sympy')
5*e - 1

Eric. 

[Oscar Benjamin]

The NoneType error is presumably a bug in the sage wrapper code.
Possibly related is that Maxima cannot compute the sum with its
default algorithm. It does have a simplify_sum function that can do it
though:

(%i19) load (simplify_sum);
(%o19) "/usr/share/maxima/5.45.1/share/solve_rec/simplify_sum.mac"
(%i20) sum((4*n + 1)/factorial(n), n, 1, inf), simpsum;
(%o20) 'sum((4*n+1)/n!,n,1,inf)
(%i21) simplify_sum(%);
(%o21) 4*gamma_incomplete_lower(2,-1)+10*sqrt(%e)*sinh(1/2)

This is an indirect representation of 5*e - 1 as returned by SymPy.

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[Emmanuel Charpentier]

Le vendredi 9 février 2024 à 15:42:30 UTC+1, Eric Gourgoulhon a écrit :

I confirm the bug with Sage 10.3.beta7. It seems to be linked with the Maxima interface. 

Meanwhile, a workaround is to use the SymPy interface: 

sage: sum((4*n+1)/factorial(n), n, 1, oo, algorithm='sympy')
5*e - 1

FWIW, algorithms giac (and even mathematica) also work.

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