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 A319538 Numbers k such that k divides 2^(2*k+1) - 1. 0
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Sequence is infinite because 2^A187787(t) - 1 is a term for all t >= 1. LINKS MATHEMATICA Select[Range[10^5], Mod[2^(2 # + 1) - 1, #] == 0 &] (* Michael De Vlieger, Sep 24 2018 *) PROG (PARI) isok(n) = Mod(2, n)^(2*n+1)==1; CROSSREFS Cf. A187787, A296369, A319222. Sequence in context: A193186 A114939 A193224 * A290974 A145107 A231488 Adjacent sequences:  A319535 A319536 A319537 * A319539 A319540 A319541 KEYWORD nonn AUTHOR Altug Alkan, Sep 22 2018 STATUS approved

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Last modified September 23 15:06 EDT 2020. Contains 337310 sequences. (Running on oeis4.)