a(n) = integer nearest n*x, where x = sqrt(8).

Terms

a(0) =0a(1) =3a(2) =6a(3) =8a(4) =11a(5) =14a(6) =17a(7) =20a(8) =23a(9) =25a(10) =28a(11) =31a(12) =34a(13) =37a(14) =40a(15) =42a(16) =45a(17) =48a(18) =51a(19) =54a(20) =57a(21) =59a(22) =62a(23) =65a(24) =68a(25) =71a(26) =74a(27) =76a(28) =79a(29) =82