G.f.: Sum_{n>=0} (5 + x^n)^n * x^n / (1-x)^(n+1).

Terms

a(0) =1a(1) =6a(2) =37a(3) =218a(4) =1309a(5) =7810a(6) =46797a(7) =280345a(8) =1681029a(9) =10081939a(10) =60479790a(11) =362838047a(12) =2176908951a(13) =13061074143a(14) =78365313414a(15) =470188412205