a(n) = (10*n^3 - 9*n^2 + 2*n)/3 + 1.

Terms

a(0) =1a(1) =2a(2) =17a(3) =66a(4) =169a(5) =346a(6) =617a(7) =1002a(8) =1521a(9) =2194a(10) =3041a(11) =4082a(12) =5337a(13) =6826a(14) =8569a(15) =10586a(16) =12897a(17) =15522a(18) =18481a(19) =21794a(20) =25481a(21) =29562a(22) =34057a(23) =38986a(24) =44369a(25) =50226a(26) =56577a(27) =63442a(28) =70841a(29) =78794