A058371 The sequence S defined in A058540.

0, 0, 1, 3, 12, 48, 217, 1005, 4878, 24218, 123021, 634995, 3323963, 17596131, 94053675, 506865965, 2751093957, 15025119759, 82511460766, 455331632088, 2523688452540, 14042621802676, 78415665739800, 439298161502112, 2468288819015277

Offset: 0

Author

N. J. A. Sloane, Dec 26 2000

Keywords

• nonn

Crossrefs

Cf. A058575.

Programs

Maple

spec := [ S, {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
spec:=[S,{S=Set(Union(Z,S,S),card>=2)}];[seq(combstruct[count](spec,size=n),n=0..25)]; # Vladeta Jovovic, Jun 25 2007