a(n) = 81*n^2 - 9*n.

Terms

a(0) =0a(1) =72a(2) =306a(3) =702a(4) =1260a(5) =1980a(6) =2862a(7) =3906a(8) =5112a(9) =6480a(10) =8010a(11) =9702a(12) =11556a(13) =13572a(14) =15750a(15) =18090a(16) =20592a(17) =23256a(18) =26082a(19) =29070a(20) =32220a(21) =35532a(22) =39006a(23) =42642a(24) =46440a(25) =50400a(26) =54522a(27) =58806a(28) =63252a(29) =67860