OFFSET
0,3
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
R. C. Read, The enumeration of mating-type graphs, Report CORR 89-38, Dept. Combinatorics and Optimization, Univ. Waterloo, 1989.
FORMULA
a(n) = Sum_{k=0..n} Stirling1(n, k)*2^(k^2-k). - Vladeta Jovovic, Feb 11 2003
E.g.f.: Sum_{n>=0} 2^(n*(n-1))*log(1+x)^n/n!. - Paul D. Hanna, May 20 2009
MATHEMATICA
a[0] = 1; a[n_] := Sum[StirlingS1[n , k]*2^(k^2 - k), {k, 0, n}];
Table[a[n], {n, 0, 12}] (* Jean-François Alcover, Aug 16 2019 *)
PROG
(PARI) a(n)=n!*polcoeff(sum(k=0, n, 2^(k*(k-1))*log(1+x+x*O(x^n))^k/k!), n) \\ Paul D. Hanna, May 20 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Vladeta Jovovic, Feb 11 2003
a(0)=1 prepended by Andrew Howroyd, Sep 09 2018
STATUS
approved