A058540 - OEIS

A058540

Another 3-way generalization of series-parallel networks with n unlabeled edges.

0, 1, 3, 9, 36, 144, 651, 3015, 14634, 72654, 369063, 1904985, 9971889, 52788393, 282161025, 1520597895, 8253281871, 45075359277, 247534382298, 1365994896264, 7571065357620, 42127865408028, 235246997219400, 1317894484506336

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OFFSET

0,3

COMMENTS

Compare the combstruct construction here with those for A000084 and A058534.

LINKS

Table of n, a(n) for n=0..23.

MAPLE

spec := [ N, {N=Union(Z, S, P, Q), S=Set(Union(Z, P, Q), card>=2), P=Set(Union(Z, S, Q), card>=2), Q=Set(Union(Z, S, P), card>=2)} ]; [seq(combstruct[count](spec, size=n), n=0..40)]; # N=A058540, S=A058371

CROSSREFS

Cf. A000084, A058534, A058371.

Sequence in context: A185162 A106435 A276368 * A350451 A245888 A295739

Adjacent sequences: A058537 A058538 A058539 * A058541 A058542 A058543

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 24 2000

STATUS

approved