A305005 Number of labeled clutters (connected antichains) spanning some subset of {1,...,n} without singleton edges.
1, 1, 2, 9, 111, 6829, 7783192, 2414627236071, 56130437209370100252463
Offset: 0
Keywords
Examples
The a(3) = 9 clutters: {} {{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}}
Links
Crossrefs
Formula
a(n) = A198085(n) - n + 1. - Gus Wiseman, Jun 11 2018