

A131313


Number of labeled 4arch graphs on n nodes.


0



0, 0, 0, 1, 1, 15, 1085, 216230, 92550276, 74358276300, 102660061574400, 228311514581611725, 777903709095959606875, 3900045557544532389044051, 27829438251904221299882526375, 274842860343937013061411903607000, 3668195394384971166861021308091920000
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OFFSET

1,6


LINKS

Table of n, a(n) for n=1..17.
Saverio Caminiti and Emanuele G. Fusco, On the Number of Labeled karch Graphs, Journal of Integer Sequences, Vol 10 (2007), Article 07.7.5


FORMULA

The number of labeled 4arch graphs with n>5 nodes is given by f(n,4,n41,0,4) where f is the recursive function described by the parigp code attached below.


PROG

(PARI) f(n, k, i, u, j)={ local(s=0); if (i==1, binomial(nu, j)*binomial(u, kj), for (c=0, min(k, n(i1)(u+j)), s+=f(n, k, i1, u+j, c) ); binomial(nu, j)*binomial(u, kj)*s ) }


CROSSREFS

Cf. A098721A098724, A131311A131315.
Sequence in context: A206162 A203409 A207980 * A208346 A236329 A129764
Adjacent sequences: A131310 A131311 A131312 * A131314 A131315 A131316


KEYWORD

nonn


AUTHOR

Saverio Caminiti and Emanuele G. Fusco (fusco(AT)di.uniroma1.it), Sep 18 2007


EXTENSIONS

Edited by N. J. A. Sloane, Oct 02 2007
Terms a(11) and beyond from Andrew Howroyd, Nov 07 2019


STATUS

approved



