a(n) = 2*n*a(n-1) if the parity of the ratio a(n-1)/a(n-2) is odd, otherwise (for even parity) a(n) = (2n-1)*a(n-1).
A177373
a(n) = 2*n*a(n-1) if the parity of the ratio a(n-1)/a(n-2) is odd, otherwise (for even parity) a(n) = (2n-1)*a(n-1).
Terms
- a(0) =1a(1) =2a(2) =6a(3) =36a(4) =252a(5) =2520a(6) =27720a(7) =388080a(8) =5821200a(9) =104781600a(10) =1990850400a(11) =43798708800
External references
- oeis: A177373