a(n) = 324*n^2 + 18.

Terms

a(0) =18a(1) =342a(2) =1314a(3) =2934a(4) =5202a(5) =8118a(6) =11682a(7) =15894a(8) =20754a(9) =26262a(10) =32418a(11) =39222a(12) =46674a(13) =54774a(14) =63522a(15) =72918a(16) =82962a(17) =93654a(18) =104994a(19) =116982a(20) =129618a(21) =142902a(22) =156834a(23) =171414a(24) =186642a(25) =202518a(26) =219042a(27) =236214a(28) =254034a(29) =272502