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 A122251 #2 Mar 30 2012 18:59:15
%S A122251 1,9,729,4782969,282429536481,150094635296999121,
%T A122251 6461081889226673298932241,2503155504993241601315571986085849,
%U A122251 8727963568087712425891397479476727340041449
%N A122251 Numerators of Hankel transform of 1/(3n+1) (conjecture).
%C A122251 General conjecture: numerators of Hankel transform of 1/(p*n+1) are given by (p^2)^sum{k=1..n, sum{j=0..n, floor(k/p^j)}}, for prime p.
%F A122251 a(n)=9^A122250(n); a(n)=9^sum{k=1..n, sum{j=0..n, floor(k/3^j)}};
%Y A122251 Cf. A122249.
%K A122251 easy,nonn
%O A122251 0,2
%A A122251 _Paul Barry_, Aug 27 2006