53501860domain: NAppears in sequencesa(n) = Sum_{k <= n/2 } binomial(n-2k, 3k).at n=36A137356Number of compositions of 5*n-2 into parts 3 and 5.at n=21A369847a(n) = Sum_{k=0..floor(2*n/5)} binomial(2*n-2*k,3*k).at n=18A392401a(n) = Sum_{k=0..floor(2*n/3)} binomial(2*k,2*n-3*k).at n=27A392428