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%I #11 Apr 19 2016 01:07:35
%S 1,3,15,216,255,1080,1728,8640,18360,19344,65535,146880,182880,309504,
%T 1226400,2967888,3456000,4718520,7132320,14738400,22866096,23408640,
%U 37748160,46835712,47486208,58752000,76658400,79233024,124416000,174182400,297198720
%N Numbers such that UnitaryPhi(2*UnitaryPhi(n)) = n.
%C Odd terms are of the form Product_{0<=i<=m} F_i, 0<=m<=4, where F_i is a Fermat prime 2^(2^i)+1.
%C Contains also 1226400, 3456000, 14738400, 174182400, and 4294967295.
%H Donovan Johnson, <a href="/A117820/b117820.txt">Table of n, a(n) for n = 1..41</a> (terms < 2^35)
%e a(11) = 3*5*17*257.
%Y Cf. A047994.
%K nonn
%O 1,2
%A _Yasutoshi Kohmoto_, Apr 30 2006
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