A058534 A 3-way generalization of series-parallel networks with n unlabeled edges.

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

Offset: 0

Author

N. J. A. Sloane, Dec 24 2000

Keywords

• nonn

Comments

Compare the combstruct construction here with that for A000084.

Crossrefs

Cf. A000084, A058540, A000669, A058561.

Programs

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