A304986 Number of labeled clutters (connected antichains) spanning some subset of {1,...,n}, if clutters of the form {{x}} are allowed for any vertex x.

1, 2, 4, 12, 115, 6834, 7783198, 2414627236078, 56130437209370100252471

Offset: 0

Author

Gus Wiseman, May 23 2018

Keywords

• nonn

Examples

			The a(3) = 12 clutters:
  {}
  {{1}}
  {{2}}
  {{3}}
  {{1,2}}
  {{1,3}}
  {{2,3}}
  {{1,2,3}}
  {{1,2},{1,3}}
  {{1,2},{2,3}}
  {{1,3},{2,3}}
  {{1,2},{1,3},{2,3}}
		

Crossrefs

Cf. A048143, A198085, A261006, A304912, A304981, A304982, A304983, A304984, A304985, A304986.

Formula

a(n > 0) = A198085(n) + 1.

a(n) = A305005(n) + n.