%I A087634
%S A087634 2,3,5,7,11,13,23,29,37,41,43,53,67,73,79,83,89,97,113,127,131,139,163,
%T A087634 173,179,191,193,199,233,239,251,277,281,293,307,359,373,409,419,431,
%U A087634 433,443,487,491,499,509,577,593,619,641,653,659,673,683,709,719,727
%N A087634 Primes p such that the equation phi(k) = 4p has a solution, where phi 
               is the totient function.
%C A087634 Except for p=2, the complement of A043297. Note that for primes p < 1000, 
               we need to check for solutions k < 18478. The equation phi(k) = 2p 
               has solutions for Sophie Germain primes, A005384
%H A087634 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               TotientFunction.html">Totient Function</a>
%t A087634 t=Table[EulerPhi[n], {n, 3, 20000}]; Union[Select[t, Mod[ #, 4]==0&&PrimeQ[ 
               #/4]&& #/4<1000&]/4]
%Y A087634 Cf. A005384, A043297.
%Y A087634 Sequence in context: A067910 A075430 A095080 this_sequence A038970 A079149 
               A024694
%Y A087634 Adjacent sequences: A087631 A087632 A087633 this_sequence A087635 A087636 
               A087637
%K A087634 nonn
%O A087634 1,1
%A A087634 T. D. Noe (noe(AT)sspectra.com), Oct 24 2003