a(n) = 729*n^2 - 27.

Terms

a(0) =702a(1) =2889a(2) =6534a(3) =11637a(4) =18198a(5) =26217a(6) =35694a(7) =46629a(8) =59022a(9) =72873a(10) =88182a(11) =104949a(12) =123174a(13) =142857a(14) =163998a(15) =186597a(16) =210654a(17) =236169a(18) =263142a(19) =291573a(20) =321462a(21) =352809a(22) =385614a(23) =419877a(24) =455598a(25) =492777a(26) =531414a(27) =571509a(28) =613062a(29) =656073