a(n) = n! * Sum_{j=0..floor(n/2)} (-1)^j/binomial(n,j).
A024420
a(n) = n! * Sum_{j=0..floor(n/2)} (-1)^j/binomial(n,j).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =4a(4) =22a(5) =108a(6) =612a(7) =4416a(8) =36576a(9) =331200a(10) =3319200a(11) =36806400a(12) =445046400a(13) =5813579520a(14) =81716947200
External references
- oeis: A024420