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A287119
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Squarefree composite numbers n such that p^2 - 1 divides n^2 - 1 for every prime p dividing n.
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1
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8569, 39689, 321265, 430199, 564719, 585311, 608399, 7056721, 11255201, 17966519, 18996769, 74775791, 75669551, 136209151, 321239359, 446660929, 547674049, 866223359, 1068433631, 1227804929, 1291695119, 2315403649, 2585930689, 7229159729, 7809974369, 8117634239
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OFFSET
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1,1
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COMMENTS
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Such numbers are odd and have at least three prime factors.
Problem: are there infinitely many such numbers?
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LINKS
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PROG
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(PARI) isok(n) = {if (issquarefree(n) && !isprime(n), my(f = factor(n)); for (k=1, #f~, if ((n^2-1) % (f[k, 1]^2-1), return (0)); ); return (1); ); } \\ Michel Marcus, May 20 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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