a(n) is the number of even permutations (of an n-set) with exactly 2 fixed points.
A145220
a(n) is the number of even permutations (of an n-set) with exactly 2 fixed points.
Terms
- a(0) =1a(1) =0a(2) =0a(3) =20a(4) =45a(5) =504a(6) =3640a(7) =33480a(8) =333585a(9) =3671360a(10) =44053416a(11) =572698620a(12) =8017774765a(13) =120266629560
External references
- oeis: A145220