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 A081917 #4 Mar 30 2012 18:58:49 %S A081917 1,1,4,28,272,3375,50976,907578,18612224,432061533,11200000000, %T A081917 320680885976,10051252125696,342302635261067,12586048547315712, %U A081917 496928474121093750,20968759865037029376,941737183946729395897 %N A081917 a(0)=1, a(n)= n^(n-2)(7n^2-3n+2)/6 (n>0). %C A081917 Main diagonal of square array defined by T(n,k)=k^n(n^3-3n^2+2n+6k^3)/(6k^3), in which rows have g.f. (1-3kx+3k^2x^2-(k^3-1)x^3)/(1-kx)^4. %H A081917 Vincenzo Librandi, <a href="/A081917/b081917.txt">Table of n, a(n) for n = 0..100</a> %Y A081917 Cf. A050407, A081913, A081914, A081915, A081916. %K A081917 easy,nonn %O A081917 0,3 %A A081917 _Paul Barry_, Mar 31 2003