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A083736
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Pseudoprimes to bases 2,5 and 7.
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1
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561, 29341, 46657, 75361, 115921, 162401, 252601, 294409, 314821, 334153, 340561, 399001, 410041, 488881, 512461, 530881, 552721, 656601, 658801, 710533, 721801, 852841, 1024651, 1141141, 1152271, 1168513, 1193221, 1461241, 1569457, 1615681
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = n-th positive integer k(>1) such that 2^(k-1) = 1 (mod k), 5^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).
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EXAMPLE
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a(1)=561 since it is the first number such that 2^(k-1) = 1 (mod k), 5^(k-1) = 1 (mod k) and 7^(k-1) = 1 (mod k).
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MATHEMATICA
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Select[Range[1, 10^5, 2], CompositeQ[#] && PowerMod[2, #-1, #] == PowerMod[5, #-1, #] == PowerMod[7, #-1, #] == 1&] (* Amiram Eldar, Jun 29 2019 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Serhat Sevki Dincer (sevki(AT)ug.bilkent.edu.tr), May 05 2003
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STATUS
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approved
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