%I
%S 1,2,3,5,12,17,65,80,473,527
%N Number of signed permutations of length n invariant under the reverse complement and avoiding (2, 1), (2, 1), (2, 1).
%F a(2k) = 2^k k! + \sum_{j=0}^{k1}(kj1)! a(2j)
%F a(2k+1) = (2^k + 1)k! + \sum_{j=0}^{k1}(kj1)! a(2j+1)
%e For n = 2, the permutations are (1, 2), (2, 1), (1, 2), (2, 1).
%K nonn
%O 0,2
%A _Andy Hardt_, Aug 04 2011
