0,2

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

J. Berman and P. Koehler, Cardinalities of finite distributive lattices, Mitteilungen aus dem Mathematischen Seminar Giessen, 121 (1976), 103-124.

G. Kreweras, Les preordres totaux compatibles avec un ordre partiel. Math. Sci. Humaines No. 53 (1976), 5-30.

Sequence in context: A003807 A011785 A003800 this_sequence A019286 A064767 A115222

Adjacent sequences: A006360 A006361 A006362 this_sequence A006364 A006365 A006366

nonn

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