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A058534 A 3-way generalization of series-parallel networks with n unlabeled edges. 3
0, 1, 3, 6, 15, 36, 99, 270, 783, 2298, 6936, 21204, 65895, 206862, 656253, 2098602, 6761028, 21917364, 71450229, 234070806, 770216253, 2544458592, 8435990916, 28060099692, 93612265143, 313153860210, 1050194570445, 3530080085868 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Compare the combstruct construction here with that for A000084.

LINKS

Table of n, a(n) for n=0..27.

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)} ]; [seq(combstruct[count](spec, size=n), n=0..40)]; # N = A058534, S=A000669

CROSSREFS

Cf. A000084, A058540, A000669, A058561.

Sequence in context: A174297 A005043 A099323 * A063778 A279374 A087124

Adjacent sequences:  A058531 A058532 A058533 * A058535 A058536 A058537

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 24 2000

STATUS

approved

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Last modified November 15 15:59 EST 2018. Contains 317239 sequences. (Running on oeis4.)