a(n) = number of permutations (p(1),p(2),p(3),...,p(n)) of (1,2,3,...n) each of which is its own inverse and is such that p(k) = n + 1 - p(n+1-k) for all k in the range 1 <= k <= n.

A135401

a(n) = number of permutations (p(1),p(2),p(3),...,p(n)) of (1,2,3,...n) each of which is its own inverse and is such that p(k) = n + 1 - p(n+1-k) for all k in the range 1 <= k <= n.