2,1

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).

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 167.

Sequence in context: A077795 A038496 A025226 this_sequence A032179 A075979 A128681

Adjacent sequences: A001191 A001192 A001193 this_sequence A001195 A001196 A001197

nonn

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