OFFSET
0,2
REFERENCES
Getu, S.; Shapiro, L. W.; Combinatorial view of the composition of functions. Ars Combin. 10 (1980), 131-145.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..396
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 157
FORMULA
E.g.f.: 1/(2-x-exp(x)).
a(n) ~ n! / ((1+c) * (2-c)^(n+1)), where c = A226571 = LambertW(exp(2)). - Vaclav Kotesovec, Jun 06 2019
a(0) = 1; a(n) = n * a(n-1) + Sum_{k=0..n-1} binomial(n,k) * a(k). - Ilya Gutkovskiy, Jul 02 2020
MATHEMATICA
With[{nn=20}, CoefficientList[Series[1/(2-x-E^x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Apr 27 2018 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Ralf Stephan, Mar 12 2004
STATUS
approved