a(n)=n+floor(r*a(n-1)), where r = golden ratio = (1+sqrt(5))/2, a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =15a(5) =29a(6) =52a(7) =91a(8) =155a(9) =259a(10) =429a(11) =705a(12) =1152a(13) =1876a(14) =3049a(15) =4948a(16) =8022a(17) =12996a(18) =21045a(19) =34070a(20) =55146a(21) =89249a(22) =144429a(23) =233714a(24) =378181a(25) =611934a(26) =990156a(27) =1602133a(28) =2592333a(29) =4194511