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

Terms

a(0) =0a(1) =3a(2) =5a(3) =8a(4) =10a(5) =13a(6) =16a(7) =18a(8) =21a(9) =24a(10) =26a(11) =29a(12) =31a(13) =34a(14) =37a(15) =39a(16) =42a(17) =45a(18) =47a(19) =50a(20) =52a(21) =55a(22) =58a(23) =60a(24) =63a(25) =65a(26) =68a(27) =71a(28) =73a(29) =76