a(n+1) is the smallest odd m whose cototient equals a(n).

Terms

a(0) =1a(1) =3a(2) =9a(3) =21a(4) =45a(5) =117a(6) =297a(7) =585a(8) =1521a(9) =3105a(10) =6993a(11) =14553a(12) =43653a(13) =90885a(14) =185925a(15) =397125a(16) =847125a(17) =1813125a(18) =3238725a(19) =7556829a(20) =17253789a(21) =36910365a(22) =94571997a(23) =220301277a(24) =475043037a(25) =47979336637a(26) =183450404605a(27) =525019294077