7573069568

Appears in sequences

• a(n) = 2*(a(n-1) + (n-1)*a(n-2)) for n >= 2 with a(0) = 1.at n=15A000898
• 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.at n=30A135401
• 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.at n=31A135401