a(n) = 2*binomial(n+4, 4) + n + 4.

Terms

a(0) =6a(1) =15a(2) =36a(3) =77a(4) =148a(5) =261a(6) =430a(7) =671a(8) =1002a(9) =1443a(10) =2016a(11) =2745a(12) =3656a(13) =4777a(14) =6138a(15) =7771a(16) =9710a(17) =11991a(18) =14652a(19) =17733a(20) =21276a(21) =25325a(22) =29926a(23) =35127a(24) =40978a(25) =47531a(26) =54840a(27) =62961a(28) =71952a(29) =81873