A027436 G.f. f(x) = Sum_{n>=1} a(n)*x^n satisfies f(f(x)) = x*(1 + 4*x).

0, 1, 2, -4, 16, -80, 432, -2304, 10944, -35328, -74112, 2736384, -30853632, 238663680, -1247457280, 2201247744, 32530722816, -320650199040, 156266184704, 18314630348800, -20667999748096, -3428200020508672

Offset: 0

Author

Jonathan Deane

Keywords

• sign

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..486

Crossrefs

Cf. A097088, A097089.

Formula

a(n) = 4^(n-1) * A097088(n) / 2^A097089(n).

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

Extensions

Added a(0)=0 (sum in title starts at a(1)), Henry Bottomley, Apr 20 2011