4,1

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).

J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 142.

Sequence in context: A118328 A079414 A005946 this_sequence A100413 A160344 A163691

Adjacent sequences: A000524 A000525 A000526 this_sequence A000528 A000529 A000530

nonn

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