a(n) = ceiling(Pi*n^3).

Terms

a(0) =0a(1) =4a(2) =26a(3) =85a(4) =202a(5) =393a(6) =679a(7) =1078a(8) =1609a(9) =2291a(10) =3142a(11) =4182a(12) =5429a(13) =6903a(14) =8621a(15) =10603a(16) =12868a(17) =15435a(18) =18322a(19) =21549a(20) =25133a(21) =29095a(22) =33452a(23) =38224a(24) =43430a(25) =49088a(26) =55217a(27) =61836a(28) =68965a(29) =76621