154603domain: NAppears in sequencesa(n) = Sum_{k <= n/2 } binomial(n-2k, 3k).at n=25A137356Number of compositions (ordered partitions) of n into prime divisors of n.at n=75A284463Number of compositions of 5*n into parts 3 and 5.at n=15A369845a(n) = Sum_{k=0..floor(2*n/3)} binomial(2*k+1,2*n-3*k).at n=18A392454