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 A186270 #9 Mar 18 2024 05:53:27
%S A186270 1,1,10,280,38080,18887680,39286374400,319319651123200,
%T A186270 10504339243348787200,1374135642457914946355200,
%U A186270 721146385161913763847208960000,1511615130036671973985522422906880000,12683442560532981918553467630898150113280000,425533759542581882449393472981756918078982062080000
%N A186270 a(n)=Product{k=0..n, A003665(k)}.
%C A186270 a(n) is the determinant of the symmetric matrix (if(j<=floor((i+j)/2), 2^j*J(j+1),
%C A186270 2^i*J(i+1)))_{0<=i,j<=n}, where J(n)=A001045(n).
%F A186270 a(n)=Product{k=0..n, 4^k/2+(-2)^k/2}=Product{k=0..n, sum{j=0..floor(k/2), binomial(n,2k)*9^k}}.
%F A186270 a(n) ~ c * 2^(n^2 - 1), where c = 2*QPochhammer(1/2, -1/2) = 1.1373978925308570119099534741488893085817049027787180586386880920367... . - _Vaclav Kotesovec_, Jul 11 2015, updated Mar 18 2024
%e A186270 a(3)=280 since det[1, 1, 1, 1; 1, 2, 2, 2; 1, 2, 12, 12; 1, 2, 12, 40]=280.
%t A186270 Table[Product[4^k/2+(-2)^k/2,{k,0,n}],{n,0,15}] (* _Vaclav Kotesovec_, Jul 11 2015 *)
%Y A186270 Cf. A186269.
%K A186270 nonn,easy
%O A186270 0,3
%A A186270 _Paul Barry_, Feb 16 2011