180388626432domain: NAppears in sequencesNumerator of 2n/v(n)^2, where v(1) = 0, v(2) = 1, and v(n) = v(n-1)/(n-2) + v(n-2) for n >= 3; limit of 2n/v(n)^2 is Pi.at n=20A239224p-INVERT of (1,1,1,1,1,...), where p(S) = (1 - 3*S)^2.at n=16A291004