253624579domain: NAppears in sequencesNumber of nX1 0..2 arrays with every row and column least squares fitting to a zero slope straight line, with a single point array taken as having zero slope.at n=21A223743a(n) is the constant term in expansion of Product_{k=1..n} (x^(2*k-1) + 1 + 1/x^(2*k-1))^2.at n=11A369387