a(n) = (4*n^3 - 12*n^2 + 14*n + 3)/3.

Terms

a(0) =1a(1) =3a(2) =5a(3) =15a(4) =41a(5) =91a(6) =173a(7) =295a(8) =465a(9) =691a(10) =981a(11) =1343a(12) =1785a(13) =2315a(14) =2941a(15) =3671a(16) =4513a(17) =5475a(18) =6565a(19) =7791a(20) =9161a(21) =10683a(22) =12365a(23) =14215a(24) =16241a(25) =18451a(26) =20853a(27) =23455a(28) =26265a(29) =29291