263576791domain: NAppears in sequencesa(n) = Sum_{k <= n/2 } binomial(n-2k, 3k).at n=39A137356Expansion of 1/(1 - x^3/(1-x)^5).at n=24A369804a(n) = Sum_{k=0..floor((2*n+1)/3)} binomial(2*k+1,2*n-3*k+1).at n=28A391600