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 A241543 #8 Jul 17 2016 07:15:20 %S A241543 1,1,2,2,2,6,4,20,10,70,28,252,84,924,264,3432,858,12870,2860,48620, %T A241543 9724,184756,33592,705432,117572,2704156,416024,10400600,1485800, %U A241543 40116600,5348880,155117520,19389690,601080390,70715340,2333606220,259289580,9075135300 %N A241543 a(n) = A241477(n, n). %C A241543 See A241477 and A232500 for the combinatorial definitions. %F A241543 a(n) = 2*floor(n/2)*(n-2)!/floor(n/2)!^2 for n>=2. %F A241543 a(n+2) = 2*A057977(n) for n>=0. - _Peter Luschny_, Jul 17 2016 %p A241543 A241543 := proc(n) %p A241543 if n < 2 then 1 %p A241543 else 2*iquo(n,2)*(n-2)!/iquo(n,2)!^2 %p A241543 fi end: %p A241543 seq(A241543(n), n=0..37); %Y A241543 Cf. A057977, A241477, A232500. %K A241543 nonn %O A241543 0,3 %A A241543 _Peter Luschny_, Apr 25 2014