A001827 Related to graded partially ordered sets. (Formerly M3591 N1456)

1, 4, 22, 166, 1726, 24814, 494902, 13729846, 531077086, 28697950174, 2170176736102, 230007989092006, 34211282155446286, 7149766552058591374, 2101690590380890192342, 869808621195903097079446, 507261036269544624540347326

Offset

0,2

Comments

Corresponds to the numbers c(4,n) in the Klarner paper. - Sean A. Irvine, Sep 24 2015

References

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

John Cerkan, Table of n, a(n) for n = 0..112

D. A. Klarner, The number of graded partially ordered sets, J. Combin. Theory, 6 (1969), 12-19. [Annotated scanned copy]

D. A. Klarner, The number of graded partially ordered sets, J. Combin. Theory, 6 (1969), 12-19.

Index entries for sequences related to posets

Formula

a(n) = Sum_{p+q+r+s=n} (n!/p!q!r!s!) 2^(pq+qr+rs) where (p,q,r,s) is any nonnegative composition of n. - Sean A. Irvine, Sep 24 2015

Crossrefs

Column k=4 of A361950.

Cf. A000684, A001828, A001829, A001830, A047863.

Sequence in context: A247249 A368319 A113351 * A363115 A368285 A350268

Adjacent sequences: A001824 A001825 A001826 * A001828 A001829 A001830

Keyword

nonn

Author

N. J. A. Sloane

Extensions

More terms from Sean A. Irvine, Sep 24 2015

Status

approved