a(n) = 18*n^2.

Terms

a(0) =0a(1) =18a(2) =72a(3) =162a(4) =288a(5) =450a(6) =648a(7) =882a(8) =1152a(9) =1458a(10) =1800a(11) =2178a(12) =2592a(13) =3042a(14) =3528a(15) =4050a(16) =4608a(17) =5202a(18) =5832a(19) =6498a(20) =7200a(21) =7938a(22) =8712a(23) =9522a(24) =10368a(25) =11250a(26) =12168a(27) =13122a(28) =14112a(29) =15138