a(n) = (2*n - 7)*n^2.

Terms

a(0) =0a(1) =-5a(2) =-12a(3) =-9a(4) =16a(5) =75a(6) =180a(7) =343a(8) =576a(9) =891a(10) =1300a(11) =1815a(12) =2448a(13) =3211a(14) =4116a(15) =5175a(16) =6400a(17) =7803a(18) =9396a(19) =11191a(20) =13200a(21) =15435a(22) =17908a(23) =20631a(24) =23616a(25) =26875a(26) =30420a(27) =34263a(28) =38416a(29) =42891