a(n) = (1/6)*n^5 - (19/8)*n^4 + (51/4)*n^3 - (253/8)*n^2 + (445/12)*n - 14.

Terms

a(0) =2a(1) =3a(2) =5a(3) =7a(4) =11a(5) =42a(6) =168a(7) =520a(8) =1312a(9) =2861a(10) =5607a(11) =10133a(12) =17185a(13) =27692a(14) =42786a(15) =63822a(16) =92398a(17) =130375a(18) =179897a(19) =243411a(20) =323687a(21) =423838a(22) =547340a(23) =698052a(24) =880236a(25) =1098577a(26) =1358203a(27) =1664705a(28) =2024157a(29) =2443136