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A319222 Numbers k such that k divides 2^(2k+1) + 1. 1
1, 3, 129, 2537, 51889, 101617, 226873, 270427, 653467, 945667, 1740979, 5819937, 6520987, 9828587, 15452867, 24950857, 51377539, 89519449, 108627601, 135776371, 160126609, 296338873, 310026163, 400431289, 641706243, 643359937, 678257563, 803419697, 902661523, 952431331, 1004273987, 1243893697, 1796055907 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Also, numbers k such that 4^k == -1/2 (mod k) (cf. A296369). - Max Alekseyev, Sep 15 2018
If k is in the sequence, and m is another divisor of 2^(2*k+1)+1 and is coprime to k, then m*k is in the sequence. - Robert Israel, Sep 14 2018
LINKS
MAPLE
filter:= n -> 2 &^ (2*n+1)+1 mod n = 0:
select(filter, [$1..10^7]); # Robert Israel, Sep 14 2018
PROG
(PARI) is_A319222(n) = Mod(2, n)^(2*n+1)==-1;
CROSSREFS
Sequence in context: A243213 A264582 A108713 * A300543 A300970 A300927
KEYWORD
nonn
AUTHOR
Altug Alkan, Sep 13 2018
STATUS
approved

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Last modified July 24 12:13 EDT 2024. Contains 374583 sequences. (Running on oeis4.)