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A319505 Numbers k such that 2^(k*(k+1)/2) == -1 (mod k^2). 0

%I

%S 1,389993,476729,2927297,3048569,3862529,3914049,4755729,5077209,

%T 7460409,9009489,9314009,11066649,11981409,12928289,13342769,15371609,

%U 15574449,22975249,34429449,44876649,57046209,66358417,66963369,79552209,83006769,96783929,99127313,118462737,126209609,128566689,139745969

%N Numbers k such that 2^(k*(k+1)/2) == -1 (mod k^2).

%o (PARI) isok(n) = Mod(2, n^2)^(n*(n+1)/2)==-1;

%Y Cf. A006125, A077816, A126884.

%K nonn

%O 1,2

%A _Altug Alkan_, Sep 21 2018

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Last modified September 25 22:56 EDT 2022. Contains 356986 sequences. (Running on oeis4.)