1,2

Number of bipartitional relations on a set of cardinality n. - Ralf Stephan, Apr 27 2003

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

Wagner, Carl G.; Enumeration of generalized weak orders. Arch. Math. (Basel) 39 (1982), no. 2, 147-152.

T. D. Noe, Table of n, a(n) for n=1..100

P. Blasiak, K. A. Penson and A. I. Solomon, Dobinski-type relations and the log-normal distribution.

C. G. Bower, Transforms

Foata, D. and Krattenthaler, C., Graphical Major Indices, II, Seminaire Lotharingien de Combinatoire, B34k, 16 pp., 1995.

D. Foata and D. Zeilberger, [math/9406220] The Graphical Major Index

a(n) = sum(k^n*(2/3)^k, k = 0..infinity)/3; a(n) = sum(stirling2(n, k)*(2^k)*k!, k = 0..n); E.g.f. : 1/(3-2*exp(x))

Stirling transform of A000165. - Karol A. Penson (penson(AT)lptl.jussieu.fr), Jan 25 2002

"AIJ" (ordered, indistinct, labeled) transform of 2, 2, 2, 2...

Recurrence: a(n) = 2*Sum_{k=1..n} binomial(n, k)*a(n-k), a(0)=1. - Vladeta Jovovic (vladeta(AT)eunet.rs), Mar 27 2003

E.g.f.: 1/(3 - 2e^x).

Cf. A004121, A004122, A000165, A000670, A032033.

Second row of array A094416 (generalized ordered Bell numbers).

Equals 2 * A050351(n) for n>0.

Sequence in context: A046863 A000698 A092881 this_sequence A086352 A005365 A059104

Adjacent sequences: A004120 A004121 A004122 this_sequence A004124 A004125 A004126

nonn,nice,easy

N. J. A. Sloane (njas(AT)research.att.com).

More terms from Christian G. Bower (bowerc(AT)usa.net)