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 A123309 #3 Mar 30 2012 18:36:59 %S A123309 1,4,32,336,4256,63072,1076128,20900032,457645984,11201485632, %T A123309 304074996512,9089787596288,297305835048096,10578368788224320, %U A123309 407327197600166304,16894650230806939776,751638529171350907808 %N A123309 Column 3 of triangle A123305. %C A123309 Triangle T=A123305 is defined by: (column k of T) = (k+1)*(column k of T^2) shifted to have an initial '1'; thus this sequence shifted left equals 4 times column 3 of T^2 (matrix square of A123305). %Y A123309 Cf. A123305; A123306, A123307, A123308; A123310, A123311. %K A123309 nonn %O A123309 0,2 %A A123309 _Paul D. Hanna_, Sep 25 2006