0,4

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 218.

V. A. Liskovets, A contribution to the enumeration of strongly connected digraphs, Dokl. AN BSSR, 17 (1973), 1077-1080, MR49#4849.

R. C. Read and R. J. Wilson, An Atlas of Graphs, Oxford, 1998.

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.

R. W. Robinson, Table of n, a(n) for n = 0..18

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Cf. A003030.

Sequence in context: A163011 A142162 A082546 this_sequence A054953 A111834 A006471

Adjacent sequences: A035509 A035510 A035511 this_sequence A035513 A035514 A035515

nonn,nice

R. C. Read (rcread(AT)math.uwaterloo.ca)

a(12) and a(13) added by N. J. A. Sloane (njas(AT)research.att.com) from the Robinson report, Oct 17 2006