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 A131792 #9 Jun 20 2025 15:42:23
%S A131792 1,1,2,6,21,76,280,1045,3936,14925,56892,217791,836706,3224157,
%T A131792 12456225,48232162,187131664,727309265,2831193004,11036424667,
%U A131792 43076087806,168322335246,658416150496,2577945422410,10102468839284,39621592646545
%N A131792 Main diagonal of triangle A131791: a(n) = A131791(n,n) for n>=0.
%C A131792 Row n of triangle A131791 has 2^n terms for n>=0, where row sums and central terms of A131791 equals A028361: Product_{i=0..n-1} (2^i + 1).
%F A131792 a(n) = [x^n] Product_{j=0..n-1} [ (1 - x^(2^j+1) ) / (1-x) ] for n>0, with a(0)=1. - _Max Alekseyev_, Aug 30 2007.
%o A131792 (PARI) {a(n)=if(n==0,1,polcoeff(prod(j=0,n-1,(1-x^(2^j+1))/(1-x)+x*O(x^n)),n))} \\ _Max Alekseyev_, Aug 30 2007
%o A131792 (PARI) {T(n,k)=if(n==0,1,polcoeff(prod(j=0,n-1,(1-x^min(2^j+1,k+1))/(1-x)+x*O(x^k)),k))} \\ _Martin Fuller_, Aug 31 2007
%K A131792 nonn
%O A131792 0,3
%A A131792 _Paul D. Hanna_, Jul 15 2007
%E A131792 More terms from _Max Alekseyev_, Aug 30 2007.