20314880

Appears in sequences

• a(0)=1; a(1)=0; a(n) = 2*(n-1)*(a(n-1) + a(n-2)).at n=9A053871
• Triangle read by rows: T(n, k) = number of matchings of 2n people with partners (of either sex) such that exactly k couples are left together.at n=45A055140
• Triangle read by rows: T(n, k) = (T(n-1, k-1) + T(n-1, k)) * 2 * n with initial values T(n, 0) = Sum_{i=0..n} (-1)^(n-i) * binomial(n, i) * A001147(i) and T(i, j) = 0 if j > i.at n=37A372260