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 A027436 #24 May 03 2024 12:12:51
%S A027436 0,1,2,-4,16,-80,432,-2304,10944,-35328,-74112,2736384,-30853632,
%T A027436 238663680,-1247457280,2201247744,32530722816,-320650199040,
%U A027436 156266184704,18314630348800,-20667999748096,-3428200020508672
%N A027436 G.f. f(x) = Sum_{n>=1} a(n)*x^n satisfies f(f(x)) = x*(1 + 4*x).
%H A027436 Seiichi Manyama, <a href="/A027436/b027436.txt">Table of n, a(n) for n = 0..486</a>
%F A027436 a(n) = 4^(n-1) * A097088(n) / 2^A097089(n).
%F A027436 T(n,m) = if n=m then 1 else (binomial(m,n-m)*4^(n-m)-sum(i=m+1..n-1, T(n,i)*T(i,m)))/2. a(n) = T(n,1). - _Vladimir Kruchinin_, Nov 08 2011
%Y A027436 Cf. A097088, A097089.
%K A027436 sign
%O A027436 0,3
%A A027436 _Jonathan Deane_
%E A027436 Added a(0)=0 (sum in title starts at a(1)), _Henry Bottomley_, Apr 20 2011