a(n) = 28*n^2.

Terms

a(0) =0a(1) =28a(2) =112a(3) =252a(4) =448a(5) =700a(6) =1008a(7) =1372a(8) =1792a(9) =2268a(10) =2800a(11) =3388a(12) =4032a(13) =4732a(14) =5488a(15) =6300a(16) =7168a(17) =8092a(18) =9072a(19) =10108a(20) =11200a(21) =12348a(22) =13552a(23) =14812a(24) =16128a(25) =17500a(26) =18928a(27) =20412a(28) =21952a(29) =23548