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%I #6 Mar 30 2012 17:22:10
%S 2,4,8,14,25,41,74,124,222,390,706,1262,2324,4244,7869,14607,27337,
%T 51243,96665,182666,346647,659206,1257287,2402569,4601771,8828741,
%U 16969511,32665154,62972932
%N a(n) = 2^n - A210109(n).
%C This is the number of binary sequences of length n that are not 3-divided. The number that are not 2-divided turned out, surprisingly, to be A000031, so this also seems worth including.
%Y Cf. A210109, A000031, A209970.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Mar 17 2012