Ceiling(4*Pi*n^2).

Terms

a(0) =13a(1) =51a(2) =114a(3) =202a(4) =315a(5) =453a(6) =616a(7) =805a(8) =1018a(9) =1257a(10) =1521a(11) =1810a(12) =2124a(13) =2464a(14) =2828a(15) =3217a(16) =3632a(17) =4072a(18) =4537a(19) =5027a(20) =5542a(21) =6083a(22) =6648a(23) =7239a(24) =7854a(25) =8495a(26) =9161a(27) =9853a(28) =10569a(29) =11310