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A058561 A 3-way generalization of series-parallel networks with n labeled edges. 2
0, 1, 3, 12, 78, 708, 8256, 117624, 1980096, 38456736, 846413472, 20819693568, 565998548352, 16852047061632, 545372109629184, 19061178127458816, 715541912895773184, 28713061759257037824, 1226513716981332031488 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..18.

MAPLE

spec := [ N, {N=Union(Z, S, P, Q), S=Set(Union(Z, P), card>=2), P=Set(Union(Z, Q), card>=2), Q=Set(Union(Z, S), card>=2)}, labeled ]; [seq(combstruct[count](spec, size=n), n=0..40)]; # N = A058561, S=A000311

CROSSREFS

Cf. A058534, A000311, A006351.

Sequence in context: A060946 A121421 A108043 * A058107 A213139 A023879

Adjacent sequences:  A058558 A058559 A058560 * A058562 A058563 A058564

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 26 2000

STATUS

approved

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Last modified December 13 18:19 EST 2018. Contains 318086 sequences. (Running on oeis4.)