a(n) = 15*n^2.

Terms

a(0) =0a(1) =15a(2) =60a(3) =135a(4) =240a(5) =375a(6) =540a(7) =735a(8) =960a(9) =1215a(10) =1500a(11) =1815a(12) =2160a(13) =2535a(14) =2940a(15) =3375a(16) =3840a(17) =4335a(18) =4860a(19) =5415a(20) =6000a(21) =6615a(22) =7260a(23) =7935a(24) =8640a(25) =9375a(26) =10140a(27) =10935a(28) =11760a(29) =12615