a(n) = round(n*phi^3), where phi is the golden ratio, A001622.

Terms

a(0) =0a(1) =4a(2) =8a(3) =13a(4) =17a(5) =21a(6) =25a(7) =30a(8) =34a(9) =38a(10) =42a(11) =47a(12) =51a(13) =55a(14) =59a(15) =64a(16) =68a(17) =72a(18) =76a(19) =80a(20) =85a(21) =89a(22) =93a(23) =97a(24) =102a(25) =106a(26) =110a(27) =114a(28) =119a(29) =123