%I A071008
%S A071008 2,4,16,256,65536,3110400,4294967296
%N A071008 Numbers n such that uphi(uphi(n))=n/2.
%C A071008 If n=Product p_i^r_i then uphi(n)=Product ( p_i^r_i-1); for example uphi(12)=(4-1)*(3-1)=6
%C A071008 If 2^n+1 is a Fermat prime then 2^(2*n) is a solution of the equation.
%e A071008 Factorizations: 2, 2^2, 2^4. 2^8, 2^16, 2^9*3^5*5^2, 2^32
%Y A071008 Cf. A030163.
%Y A071008 Sequence in context: A050472 A109457 A105788 this_sequence A001146 A114641 
               A152690
%Y A071008 Adjacent sequences: A071005 A071006 A071007 this_sequence A071009 A071010 
               A071011
%K A071008 nonn
%O A071008 1,1
%A A071008 Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp)