1,2

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

Hanlon, Phil; Counting interval graphs. Trans. Amer. Math. Soc. 272 (1982), no. 2, 383-426.

P. J. Hanlon, personal communication.

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980.

R. W. Robinson, Table of n, a(n) for n = 1..30

Sequence in context: A143217 A139017 A085657 this_sequence A058862 A140722 A116976

Adjacent sequences: A005212 A005213 A005214 this_sequence A005216 A005217 A005218

nonn

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