a(n) = ((2*n-1)!! + (-1)^((n-1)*(n-2)/2))/2.
A220092
a(n) = ((2*n-1)!! + (-1)^((n-1)*(n-2)/2))/2.
Terms
- a(0) =1a(1) =2a(2) =7a(3) =52a(4) =473a(5) =5198a(6) =67567a(7) =1013512a(8) =17229713a(9) =327364538a(10) =6874655287a(11) =158117071612
External references
- oeis: A220092