a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/2^k.
A356632
a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/2^k.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =9a(4) =48a(5) =330a(6) =2880a(7) =29610a(8) =362880a(9) =5148360a(10) =83462400a(11) =1535549400a(12) =31614105600a(13) =724183059600
External references
- oeis: A356632