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 A375231 #7 Aug 06 2024 21:55:59
%S A375231 1,1,3,9,19,82,229,1313,4581,32826,137431,1181737,5772103,57905114,
%T A375231 323237769,3705927297,23273119369,300180111058,2094580743211,
%U A375231 30018011105801,230403881753211,3632179343801922,30413312391423853,523033825507476769,4744476733062121069,88392716510763573962
%N A375231 Interleaving A006040 and A228229.
%C A375231 Conjecture: a(n) is the permanent of the n X n matrix whose generic element is given by M_{i,j} = 1 if i = j or i + j = 1 (mod 2), with i,j in [n].
%F A375231 a(n) = A006040((n+1)/2) for odd n.
%F A375231 a(n) = A228229(n/2) for even n.
%t A375231 A006040[n_]:=Sum[(n!/(n - k)!)^2, {k, 0, n}]; A228229[n_]:= n!*(n + 1)!*Sum[ 1/(k!*(k + 1)!),{k,0,n}]; a[n_]:=If[OddQ[n],A006040[(n+1)/2],A228229[n/2]]; Array[a,26,0]
%Y A375231 Cf. A006040, A078126 (determinant), A228229.
%K A375231 nonn
%O A375231 0,3
%A A375231 _Stefano Spezia_, Aug 06 2024