1,2

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).

M. A. Sainte-Lagu\"{e}, Les R\'{e}seaux (ou Graphes)}, M\'{e}morial des Sciences Math\'{e}matiques, Fasc. 18, Gauthier-Villars, Paris, 1926, p. 49.

Sequence in context: A019238 A157404 A135704 this_sequence A019428 A055252 A116414

Adjacent sequences: A002561 A002562 A002563 this_sequence A002565 A002566 A002567

nonn

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