a(n) = 6*binomial(n,4) + 6*binomial(n,3) + 4*binomial(n,2) + 2*n + 1.

Terms

a(0) =1a(1) =3a(2) =9a(3) =25a(4) =63a(5) =141a(6) =283a(7) =519a(8) =885a(9) =1423a(10) =2181a(11) =3213a(12) =4579a(13) =6345a(14) =8583a(15) =11371a(16) =14793a(17) =18939a(18) =23905a(19) =29793a(20) =36711a(21) =44773a(22) =54099a(23) =64815a(24) =77053a(25) =90951a(26) =106653a(27) =124309a(28) =144075a(29) =166113