1,4

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

Popular Computing, Vol. 1 (No. 7, 1973), front cover and page 2.

T. R. Parkin, personal communication.

M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. Simon and Schuster, NY, 1969, p. 189.

Illustration showing that a(6) = 37.

Cf. A003213.

Sequence in context: A066172 A018353 A081851 this_sequence A147760 A154148 A153376

Adjacent sequences: A006064 A006065 A006066 this_sequence A006068 A006069 A006070

nonn,nice

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