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 A165680 #7 Jun 02 2025 02:05:18 %S A165680 1,1,1,1,1,1,1,1,1,2,1,1,1,2,6,1,1,1,2,6,24,1,1,1,2,6,24,120,1,1,1,2, %T A165680 6,24,120,720,1,1,1,2,6,24,120,720,5040,1,1,1,2,6,24,120,720,5040, %U A165680 40320,1,1,1,2,6,24,120,720,5040,40320,362880 %N A165680 Triangle of the divisors of the coefficients of triangles A138771 and A165675. %F A165680 a(n) = A138771(n)/A165675(n-1). %e A165680 Triangle starts: %e A165680 1, %e A165680 1, 1, %e A165680 1, 1, 1, %e A165680 1, 1, 1, 2, %e A165680 1, 1, 1, 2, 6, %e A165680 1, 1, 1, 2, 6, 24, %e A165680 1, 1, 1, 2, 6, 24, 120, %e A165680 1, 1, 1, 2, 6, 24, 120, 720, %e A165680 1, 1, 1, 2, 6, 24, 120, 720, 5040, %e A165680 1, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, %e A165680 1, 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, %e A165680 ... %p A165680 nmax:=11: for n from 1 to nmax do a(n,1):=1 od: for n from 2 to nmax do for m from 2 to n do a(n,m):=(m-2)! od: od: for n from 1 to nmax do seq(a(n,m),m=1..n) od; %Y A165680 Cf. A138771, A165675 and A000142. %Y A165680 A000012 (3x), A007395, A010722, A010863 equal the first six left hand columns. %Y A165680 A159333 equals, for n=>-1, all right hand columns. %Y A165680 A067078 equals the row sums. %K A165680 easy,nonn,tabl %O A165680 1,10 %A A165680 _Johannes W. Meijer_, Oct 05 2009