The number of permutations of [n] with 2 cycles of length 2.
A178669
The number of permutations of [n] with 2 cycles of length 2.
Terms
- a(0) =0a(1) =3a(2) =15a(3) =45a(4) =315a(5) =3150a(6) =28350a(7) =274050a(8) =3014550a(9) =36330525a(10) =472296825a(11) =6609317715a(12) =99139765725
External references
- oeis: A178669