Second spoke of a hexagonal spiral.

Terms

a(0) =1a(1) =3a(2) =11a(3) =25a(4) =45a(5) =71a(6) =103a(7) =141a(8) =185a(9) =235a(10) =291a(11) =353a(12) =421a(13) =495a(14) =575a(15) =661a(16) =753a(17) =851a(18) =955a(19) =1065a(20) =1181a(21) =1303a(22) =1431a(23) =1565a(24) =1705a(25) =1851a(26) =2003a(27) =2161a(28) =2325a(29) =2495