a(n) = n*(8*n-1).

Terms

a(0) =0a(1) =7a(2) =30a(3) =69a(4) =124a(5) =195a(6) =282a(7) =385a(8) =504a(9) =639a(10) =790a(11) =957a(12) =1140a(13) =1339a(14) =1554a(15) =1785a(16) =2032a(17) =2295a(18) =2574a(19) =2869a(20) =3180a(21) =3507a(22) =3850a(23) =4209a(24) =4584a(25) =4975a(26) =5382a(27) =5805a(28) =6244a(29) =6699