A105974 (A001035(n) - 1)/2 where A001035 is the number of partially ordered sets ("posets") with n labeled elements.

0, 0, 1, 9, 109, 2115, 65011, 3064929, 215861689, 22255521255, 3305532624391, 698140838552949, 207432475527926749, 85925364190793529675, 49242162128564103516091, 38783585510220344176524969

Offset: 0

Author

Gerald McGarvey, Apr 28 2005

Keywords

• nonn

Comments

Conjectures: a(n) is (pre)periodic modulo m for all m, the lengths of the ending periods being given by 2*A000010(m) if m is a power of 2 and A000010(m) otherwise. A000010 is Euler's totient function.

Crossrefs

Cf. A001035, A000010, A102818.