a(n) = n*(n-1)*a(n-1)/2 + a(n-2), a(0) = a(1) = 1.
A001046
a(n) = n*(n-1)*a(n-1)/2 + a(n-2), a(0) = a(1) = 1.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =7a(4) =44a(5) =447a(6) =6749a(7) =142176a(8) =3987677a(9) =143698548a(10) =6470422337a(11) =356016927083
External references
- oeis: A001046