a(n) is the least odd number m minimizing A007947(m*(2^n-m)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =1a(6) =3a(7) =13a(8) =169a(9) =25a(10) =243a(11) =375a(12) =11a(13) =49a(14) =7a(15) =3a(16) =18225a(17) =71875a(18) =4913a(19) =1701a(20) =144027a(21) =1825a(22) =3483a(23) =2197a(24) =9156027a(25) =131989a(26) =1103a(27) =5103a(28) =38525a(29) =458703