a(n) = 3*n*(5*n-1)/2.

Terms

a(0) =6a(1) =27a(2) =63a(3) =114a(4) =180a(5) =261a(6) =357a(7) =468a(8) =594a(9) =735a(10) =891a(11) =1062a(12) =1248a(13) =1449a(14) =1665a(15) =1896a(16) =2142a(17) =2403a(18) =2679a(19) =2970a(20) =3276a(21) =3597a(22) =3933a(23) =4284a(24) =4650a(25) =5031a(26) =5427a(27) =5838a(28) =6264a(29) =6705