4,2

M. B. Dillencourt, personal communication.

J. McClellan, The question of allomorphs, J. Rec. Math., 4 (1971), 115-123.

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

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

Sequence in context: A069957 A091356 A107705 this_sequence A077865 A117353 A103422

Adjacent sequences: A002880 A002881 A002882 this_sequence A002884 A002885 A002886

nonn

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