OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..77
FORMULA
E.g.f. A(x) satisfies: A(x) = 1 + (exp(x) - 1) * A(2*x).
a(n) ~ c * n! * 2^(n*(n-1)/2), where c = 1.572986203588985421674040830458773854660492965929302012... - Vaclav Kotesovec, Apr 07 2022
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] 2^k a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 14}]
nmax = 14; A[_] = 0; Do[A[x_] = 1 + (Exp[x] - 1) A[2 x] + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x] Range[0, nmax]!
PROG
(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=0, i-1, 2^j*binomial(i, j)*v[j+1])); v; \\ Seiichi Manyama, Jun 18 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 06 2022
STATUS
approved