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

A027436

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

Terms

    a(0) =0a(1) =1a(2) =2a(3) =-4a(4) =16a(5) =-80a(6) =432a(7) =-2304a(8) =10944a(9) =-35328a(10) =-74112a(11) =2736384a(12) =-30853632a(13) =238663680a(14) =-1247457280a(15) =2201247744a(16) =32530722816a(17) =-320650199040a(18) =156266184704

External references