a(n) = 729*n^2 - 2*n.

Terms

a(0) =727a(1) =2912a(2) =6555a(3) =11656a(4) =18215a(5) =26232a(6) =35707a(7) =46640a(8) =59031a(9) =72880a(10) =88187a(11) =104952a(12) =123175a(13) =142856a(14) =163995a(15) =186592a(16) =210647a(17) =236160a(18) =263131a(19) =291560a(20) =321447a(21) =352792a(22) =385595a(23) =419856a(24) =455575a(25) =492752a(26) =531387a(27) =571480a(28) =613031a(29) =656040