0,4

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 231.

P. K. Stockmeyer, The enumeration of graphs with prescribed automorphism group, Dissertation, Univ. of Michigan, Ann Arbor, 1971.

Cf. A000273 (digraphs), A003400 (asymmetric graphs), A030242 (asymmetric relations)

Sequence in context: A001533 A143181 A081793 this_sequence A058881 A100520 A009701

Adjacent sequences: A051501 A051502 A051503 this_sequence A051505 A051506 A051507

hard,nonn,nice

Vladeta Jovovic (vladeta(AT)eunet.rs)

a(6) from Christian G. Bower (bowerc(AT)usa.net) Dec 15 1999.