a(n) = floor(surface area of a sphere with radius n).

Terms

a(0) =12a(1) =50a(2) =113a(3) =201a(4) =314a(5) =452a(6) =615a(7) =804a(8) =1017a(9) =1256a(10) =1520a(11) =1809a(12) =2123a(13) =2463a(14) =2827a(15) =3216a(16) =3631a(17) =4071a(18) =4536a(19) =5026a(20) =5541a(21) =6082a(22) =6647a(23) =7238a(24) =7853a(25) =8494a(26) =9160a(27) =9852a(28) =10568a(29) =11309