%I
%S 2,12,17,21,26,31,36,42,48,53,60,74,79,84,95,102,107,113,118,123,131,
%T 136,143,151,156,162,167,172,177,185,190,195,201,212,217,224,231,236,
%U 241,246,251,257,267,272,278,293,302,310,315,325,333,339,344,349,354
%N define u(k) as u(1)=1 u(k)=binomial(2*u(k1),u(k1)) (mod k), sequence gives values of k such that u(k)=0.
%F It seems that a(n) is asymptotic to c*n with 6.1 < c < 6.2.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Apr 23 2003
