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 A066121 #2 Mar 30 2012 18:51:35 %S A066121 1,2,1,3,2,1,4,6,2,1,5,24,12,2,1,6,120,288,24,2,1,7,720,34560,6912,48, %T A066121 2,1,8,5040,24883200,238878720,331776,96,2,1,9,40320,125411328000, %U A066121 5944066965504000,79254226206720,31850496,192,2,1,10,362880 %N A066121 Multi-level factorials: triangle with a(n,k)=a(n-1,k-1)*a(n-1,k) but with a(n,1)=n and a(n,n)=1. %e A066121 a(4,2)=a(3,1)*a(3,2)=3*2=6. Rows start 1; 2,1; 3,2,1; 4,6,2,1; ... %Y A066121 Columns include A000027, A000142, A000178, A055462, A057527, A057528. Right hand side includes A000012, A007395, A007283. Cf. A066119. %K A066121 nonn,tabl %O A066121 1,2 %A A066121 _Henry Bottomley_, Dec 05 2001