18128529domain: NAppears in sequencesa(n) = Sum_{k=0..n} C(n-k,3k).at n=30A003522Number of compositions of n such that two adjacent parts are not equal modulo 2.at n=43A062200Quintisection of 1/(1-x^3-x^4).at n=18A099101a(n) = Sum_{k=0..floor(n/2)} binomial(2*n-k,3*k).at n=15A392400