108575domain: NAppears in sequencesa(n) = Sum_{k <= n/2} binomial(n-2k, 3k+2).at n=23A137358Expansion of e.g.f. exp(arctan(1+2*x) - Pi/4).at n=10A199042Number of compositions of 5*n-2 into parts 3 and 5.at n=14A369847a(n) = Sum_{k=0..floor((2*n+1)/3)} binomial(2*k+1,2*n-3*k+1).at n=17A391600