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A270840
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Numbers n such that n^3 + 1 is a 2-pseudoprime (or Sarrus number).
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2
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12, 36, 138, 270, 546, 4800, 7560, 12840, 14700, 358200, 678480, 16139970, 22934100, 55058580, 59553720, 74371320, 113068380, 116605860, 242699310, 997521210, 1592680320, 1652749200, 3190927740, 5088964800, 6974736756, 9214178820
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OFFSET
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1,1
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COMMENTS
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Since n^3 + 1 is clearly composite (n>1), this is n such that 2^(n^3) == 1 (mod n^3+1).
There is only one n such that n + 1 is a composite number up to 10^10: 14700. - Altug Alkan, Mar 27 2016
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LINKS
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FORMULA
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PROG
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(PARI) is(n)=Mod(2, n^3+1)^(n^3)==1
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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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