4,2
M. B. Dillencourt, personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Table of n, a(n) for n=4..12.
Eric Weisstein's World of Mathematics, Skeleton
Sequence in context: A074141 A122931 A094976 * A099626 A046672 A046866
Adjacent sequences: A006866 A006867 A006868 * A006870 A006871 A006872
nonn
N. J. A. Sloane.
approved
