a(n) = number of special even permutations of 2*n+1.
A003109
a(n) = number of special even permutations of 2*n+1.
Terms
- a(0) =1a(1) =1a(2) =17a(3) =117a(4) =1413a(5) =46389a(6) =1211085a(7) =47977305a(8) =2302999889a(9) =137682614769
External references
- oeis: A003109