a(n) = n*(23*n + 1)/2.

Terms

a(0) =0a(1) =12a(2) =47a(3) =105a(4) =186a(5) =290a(6) =417a(7) =567a(8) =740a(9) =936a(10) =1155a(11) =1397a(12) =1662a(13) =1950a(14) =2261a(15) =2595a(16) =2952a(17) =3332a(18) =3735a(19) =4161a(20) =4610a(21) =5082a(22) =5577a(23) =6095a(24) =6636a(25) =7200a(26) =7787a(27) =8397a(28) =9030a(29) =9686