a(n) = (2*n-1)*(4*n-1).

Terms

a(0) =1a(1) =3a(2) =21a(3) =55a(4) =105a(5) =171a(6) =253a(7) =351a(8) =465a(9) =595a(10) =741a(11) =903a(12) =1081a(13) =1275a(14) =1485a(15) =1711a(16) =1953a(17) =2211a(18) =2485a(19) =2775a(20) =3081a(21) =3403a(22) =3741a(23) =4095a(24) =4465a(25) =4851a(26) =5253a(27) =5671a(28) =6105a(29) =6555