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

Offset: 0

Author

N. J. A. Sloane, Dec 24 2000

Keywords

• nonn

Comments

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

Crossrefs

Cf. A000084, A058534, A058371.

Programs

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