a(n) = Sum_{k=0..floor(n/3)} k^(3*(n-3*k)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =1a(5) =1a(6) =2a(7) =9a(8) =65a(9) =514a(10) =4124a(11) =33498a(12) =281829a(13) =2628658a(14) =31130220a(15) =521900363a(16) =11550872369a(17) =292093228523