A319538 Numbers k such that k divides 2^(2*k+1) - 1.
1, 7, 217, 1057, 3937, 10447, 24601, 32767, 91657, 145337, 279527, 666967, 1412113, 2484247, 2874847, 3124327, 4169137, 4472167, 9526207, 12021439, 16539337, 16646017, 19384207, 20139367, 24639727, 28127137, 28940887, 30583087, 66131279, 68068777, 70694167, 72299857, 72903847, 73498471, 87507049
Offset: 1
Keywords
Programs
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Mathematica
Select[Range[10^5], Mod[2^(2 # + 1) - 1, #] == 0 &] (* Michael De Vlieger, Sep 24 2018 *)
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PARI
isok(n) = Mod(2, n)^(2*n+1)==1;
Comments