Be professional.
State 3a - 1 problem.
So some home work, that is do some research.
What happens when starting with say, 1 thru 10?
Report your results. Make conjecture.
Part of what task? What's a_n ?
For best results with math newsgroups read
http://oakroadsystems.com/genl/unice.htm
Especially the sections on cross posting and quoting.
Polish math olympiad - still running till December, 5th?
http://www.om.edu.pl/zadania.php
http://www.om.edu.pl/zadania/om/om57_1.pdf
See also
http://groups.google.com/groups?q=author%3Alo%40iiilo.ro&start=0&scoring=d&filter=0
http://www.google.com/search?q=%22Kewin+Kazankow%22&filter=0
Someone should inform the organizers of the olympiad
about newsgroups...