1990850400

Appears in sequences

• 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).at n=10A177373
• a(0) = a(1) = 1, a(n) = n! / a(n-2).at n=19A214916