a(n) = 6*binomial(n,4) + 5*binomial(n,2) - 4*n + 5.

Terms

a(0) =1a(1) =2a(2) =8a(3) =25a(4) =65a(5) =146a(6) =292a(7) =533a(8) =905a(9) =1450a(10) =2216a(11) =3257a(12) =4633a(13) =6410a(14) =8660a(15) =11461a(16) =14897a(17) =19058a(18) =24040a(19) =29945a(20) =36881a(21) =44962a(22) =54308a(23) =65045a(24) =77305a(25) =91226a(26) =106952a(27) =124633a(28) =144425a(29) =166490