a(n) = 9*(n-2)^2 * (n^2 - 2*n - 1).

Terms

a(0) =0a(1) =18a(2) =252a(3) =1134a(4) =3312a(5) =7650a(6) =15228a(7) =27342a(8) =45504a(9) =71442a(10) =107100a(11) =154638a(12) =216432a(13) =295074a(14) =393372a(15) =514350a(16) =661248a(17) =837522a(18) =1046844a(19) =1293102a(20) =1580400a(21) =1913058a(22) =2295612a(23) =2732814a(24) =3229632a(25) =3791250a(26) =4423068a(27) =5130702a(28) =5919984