%I #22 Nov 15 2013 05:57:18
%S 7,73,127,337,487,601,881,937,1801,2593,2647,3079,3943,4057,4201,6553,
%T 7993,9199,10657,14407,15289,16759,18041,18121,20521,20809,21673,
%U 22111,24967,25111,26407,28393,28729,36793,39367,41161,42463,47737,47881,49201,49297
%N Primes p such that p^2 divides 2^(2^(p-1)-1) - 1.
%H Arkadiusz Wesolowski, <a href="/A188465/b188465.txt">Table of n, a(n) for n = 1..200</a>
%p isA188465 := proc(p) local m; if isprime(p) then m := modp(2 &^ ( (2 ^ (p-1))-1)-1,p) ; m := simplify(m) ; if m = 0 then true; else false; end if; else false; end if; end proc:
%p for i from 1 do p := ithprime(i) ; if isA188465(p) then printf("%d\n",p) ; end if; end do: # _R. J. Mathar_, Apr 10 2011
%t okQ[p_] := Module[{k = MultiplicativeOrder[2, p^2]}, PowerMod[2, p - 1, k] == 1]; Select[Prime[Range[5000]], okQ] (* _T. D. Noe_, Apr 11 2011 *)
%Y Cf. A001220.
%K nonn
%O 1,1
%A _Arkadiusz Wesolowski_, Apr 10 2011
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