a(n) = 9n^2 - n.

Terms

a(0) =8a(1) =34a(2) =78a(3) =140a(4) =220a(5) =318a(6) =434a(7) =568a(8) =720a(9) =890a(10) =1078a(11) =1284a(12) =1508a(13) =1750a(14) =2010a(15) =2288a(16) =2584a(17) =2898a(18) =3230a(19) =3580a(20) =3948a(21) =4334a(22) =4738a(23) =5160a(24) =5600a(25) =6058a(26) =6534a(27) =7028a(28) =7540a(29) =8070