A093857 Number of unlabeled ordered T_0-multigraphs with n edges.

2, 0, 2, 22, 278, 4436, 88852, 2184456, 64459628, 2239805712, 90214284410, 4157479612606, 216841733604410, 12682329307742732, 825184186612617418, 59320610243634707134, 4683176986971809187614, 403867178883936416642928, 37864927166010206186524472, 3843160755696708555996620560

Offset

0,1

Links

Table of n, a(n) for n=0..19.

Formula

E.g.f.: 2*exp((2-x)/(2*x-2))*sum(n>=0, (1-x)^(-binomial(n, 2))/n! ).

Prog

(PARI)
default(realprecision, 110);
N=50;
x='x+O(x^N);
s=2*exp((2-x)/(2*x-2))*sum(n=0, 66, (1-x)^(-binomial(n, 2))/n!);
s=serlaplace(s);
s=round(s);
Vec(s) /* show terms */
/* Joerg Arndt, Apr 28 2012 */

Crossrefs

Sequence in context: A077184 A077183 A101030 * A056949 A346235 A281326

Adjacent sequences: A093854 A093855 A093856 * A093858 A093859 A093860

Keyword

easy,nonn

Author

Goran Kilibarda, Vladeta Jovovic, May 21 2004

Extensions

Terms >=4157479612606 by Joerg Arndt, Apr 28 2012.

Status

approved