2,1

H. Sharp, Jr., Enumeration of vacuously transitive relations, Discrete Math. 4 (1973), 185-196.

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

Sequence in context: A150399 A150400 A150401 this_sequence A026558 A150402 A151295

Adjacent sequences: A003038 A003039 A003040 this_sequence A003042 A003043 A003044

nonn,more

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