a(n) = ceiling(n*phi^2), where phi is the golden ratio, A001622.

Terms

a(0) =0a(1) =3a(2) =6a(3) =8a(4) =11a(5) =14a(6) =16a(7) =19a(8) =21a(9) =24a(10) =27a(11) =29a(12) =32a(13) =35a(14) =37a(15) =40a(16) =42a(17) =45a(18) =48a(19) =50a(20) =53a(21) =55a(22) =58a(23) =61a(24) =63a(25) =66a(26) =69a(27) =71a(28) =74a(29) =76