This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A173499 #23 Apr 30 2025 09:14:40
%S A173499 0,0,2,20,204,2604,39990,720600,14913080,348678440,9090909090,
%T A173499 261535698060,8230246567620,281241170407092,10371206370520814,
%U A173499 410525522232055664,17361641481138401520,781282469559318055056,37275544492386193492506,1879498672877297909667780,99864380952380952380952380
%N A173499 Number of sequences of length n with terms from {0,1,...,n-1} such that the sum of terms is 0 modulo n and the i-th term is not i.
%H A173499 ArtOfProblemSolving forum, <a href="https://artofproblemsolving.com/community/c6h31946">45th IMO Team Selection Test Lincoln, Nebraska</a>
%F A173499 For odd n, a(n) = ((n-1)^n-n+1)/n.
%F A173499 For even n, a(n) = ((n-1)^n-1)/n.
%F A173499 a(n) = floor((n-1)^n / n). - _Alex Ratushnyak_, Aug 04 2012
%o A173499 (Python)
%o A173499 for n in range(1, 33):
%o A173499 print((n-1)**n // n, end=',')
%o A173499 # _Alex Ratushnyak_, Aug 04 2012
%Y A173499 Cf. A173500
%K A173499 nonn
%O A173499 1,3
%A A173499 _Max Alekseyev_, Feb 20 2010
%E A173499 More terms from _Michel Marcus_, Apr 30 2025