1,3

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

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 18, table 1.5.1, column 2 (divided by 2).

R. C. Read, The number of k-colored graphs on labeled nodes, Canad. J. Math., 12 (1960), 410-414.

R. C. Read, personal communication.

T. D. Noe, Table of n, a(n) for n=1..50

Reference gives generating function.

a(n)=(A047863(n)-2)/4. A diagonal of A058843.

Sequence in context: A083805 A006387 A014481 this_sequence A143342 A084270 A053677

Adjacent sequences: A000680 A000681 A000682 this_sequence A000684 A000685 A000686

nonn,nice,easy

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

More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 02 2000