%I

%S 3,15,21,51,65,95,165,255,261,273,285,295,345,387,465,507,513,565,641,

%T 837,1025,1353,1665,1731,1845,1953,1971,2013,2123,2193,2231,2325,2979,

%U 3087,3237,3591,3615,3645,3865,4097,4369,4405,4445,4655,4697,4797,4995

%N Let u(1)=1, u(n)=2^u(n-1) (mod n), sequence gives values of n such that u(n)=1.

%F Conjecture: a(n)/n^2 -> infinity

%K nonn

%O 1,1

%A _Benoit Cloitre_, Nov 24 2002