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 A110947 #10 Sep 11 2024 14:41:35
%S A110947 1,1,1,0,4,0,36,0,576,0,14400,0,518400,0,25401600,0,1625702400,0,
%T A110947 131681894400,0,13168189440000,0,1593350922240000,0,
%U A110947 229442532802560000,0,38775788043632640000,0,7600054456551997440000,0
%N A110947 a(n) = permanent of an n X n matrix M of zeros and ones defined as follows: if we concatenate the rows of M to form a vector v of length n^2, v_i = 1 only if i = 1 or a multiple of 2.
%F A110947 a(1)=a(2)=1 and for n>2: a(n)=0 if n=2*k, a(n)=k!^2 if n=2*k+1. - Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007
%o A110947 (PARI) a(n)={my(A=matrix(n,n,i,j,1-((i-1)*n+j)%2)); A[1,1]=1; matpermanent(A)} \\ Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007
%o A110947 (PARI) a(n)=if(n==2,1,if(n%2,((n-1)/2)!^2)) \\ Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007
%Y A110947 Odd-indexed terms are the same as A001044.
%K A110947 nonn
%O A110947 1,5
%A A110947 _Simone Severini_, Sep 25 2005
%E A110947 Corrected and extended by Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007