64933domain: NAppears in sequencesa(n) = Sum_{k=0..floor(n/6)} binomial(n-3k,3k).at n=26A100134p-INVERT of (0,1,0,1,0,1,...), where p(S) = 1 - S^3.at n=26A291217Expansion of (1 + x)^2/(1 - x^3*(1 + x)^3).at n=24A375321a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-3*k,3*k).at n=13A392402