5344988domain: NAppears in sequencesa(n) = Sum_{k <= n/2 } binomial(n-2k, 3k+1).at n=31A137357Number of compositions of 5*n into parts 3 and 5.at n=19A369845a(n) = Sum_{k=0..floor(2*n/3)} binomial(2*k+1,2*n-3*k).at n=23A392454