a(n) is the number of solutions to the congruence Sum_{k=1..n} x_k == 1 (mod 2n), where x_k are distinct elements of the set {0, 1, ..., 2n}, k = 1..n.
A174663
a(n) is the number of solutions to the congruence Sum_{k=1..n} x_k == 1 (mod 2n), where x_k are distinct elements of the set {0, 1, ..., 2n}, k = 1..n.
Terms
- a(0) =1a(1) =4a(2) =18a(3) =192a(4) =3000a(5) =56160a(6) =1234800a(7) =32256000a(8) =979776000a(9) =33566400000
External references
- oeis: A174663