%N The number of partitions of n in which at least one part is a multiple of 3.
%F a(n) = A000041(n)-A000726(n).
%Y Cf. A000041, A000726, A047967 (at least one multiple of 2), A295342 (at least one multiple of 4).
%A _R. J. Mathar_, Nov 20 2017