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G. T. Gilbert, M. I. Krusemeyer and L. C Larson, The Wohascum Problem Book, Math. Assoc of America, 1993, Problem 103, p. 25; Solution, pp. 163-164.
Table of n, a(n) for n=0..38.
Sequence in context: A157481 A100809 A056734 * A188802 A031141 A143263
Adjacent sequences: A019992 A019993 A019994 * A019996 A019997 A019998
R. K. Guy (computed by Marc Paulhus).