2868620domain: NAppears in sequencesp-INVERT of (1,0,0,1,0,0,1,0,0,...), where p(S) = (1 - S^2).at n=42A289918p-INVERT of (1,0,1,0,0,0,0,...), where p(S) = (1 - S)(1 + S^2).at n=41A291741a(n) = Sum_{k=0..floor(n/2)} binomial(4*k,n-2*k).at n=21A375314Expansion of 1 / ((1-x)^2 - x^6).at n=39A392541