115825domain: NAppears in sequencesa(n) = gcd(binomial(2n,n), 2^n + 1).at n=69A066975Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, 1), (-1, 0), (0, 1), (1, 0), (1, 1)}.at n=8A151318