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A331021
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Numbers k such that gcd(k^2, 2^(k-1) - 1) > k.
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2
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1093, 3511, 398945, 796797, 1592501, 1990353, 2388205, 3183909, 3581761, 4377465, 5173169, 5968873, 6165316, 10345245, 11538801, 15119469, 16313025, 17506581, 18302285, 20291545, 23076509, 23872213, 24650731, 26657177, 29442141, 36205625, 36974341, 37001329, 38194885
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OFFSET
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1,1
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COMMENTS
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Conjecture: each term is a multiple of a Wieferich prime.
Prime numbers in this sequence are the Wieferich primes A001220.
Pseudoprime (A001567) terms are 3581761, 5173169, 5968873, 23872213, 36974341, 53711113, ...
The terms of A291194 that are not in this sequence are 1194649, 2786057, 3979613, 4775317, 5571021, ....
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LINKS
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EXAMPLE
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1093 is a term since gcd(1093^2, 2^1092 - 1) = 1093^2 > 1093.
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MATHEMATICA
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seqQ[n_] := GCD[n^2, PowerMod[2, n - 1, n^2] - 1] > n; Select[Range[10^7], seqQ]
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PROG
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(PARI) isok(n) = gcd(n^2, 2^(n-1) - 1) > n; \\ Michel Marcus, Jan 07 2020
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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