131460domain: NAppears in sequencesa(n) = floor(C(2n,n)/2^n).at n=20A024502Base 5 digits are, in order, the first n terms of the periodic sequence with initial period 1,3,2,0.at n=7A037710Numbers k such that both k and k^2 are sums of a twin prime pair.at n=21A213784