3-fold convolution of A001700(n), n >= 0.

Terms

a(0) =1a(1) =9a(2) =57a(3) =312a(4) =1578a(5) =7599a(6) =35401a(7) =161052a(8) =719790a(9) =3173090a(10) =13836426a(11) =59803104a(12) =256596276a(13) =1094249019a(14) =4642178601a(15) =19605872724a(16) =82483419846a(17) =345839048094