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A053663
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Numbers k such that 2*k+1 does not divide k!+1.
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2
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1, 2, 4, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[100], !Divisible[#!+1, 2#+1]&] (* Harvey P. Dale, Sep 09 2014 *)
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PROG
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(Magma) [n: n in [1..100] | not (Factorial(n)+1) mod (2*n+1) eq 0 ]; // G. C. Greubel, May 18 2019
(Sage) [n for n in (1..100) if not Mod(factorial(n)+1, 2*n+1)==0 ] # G. C. Greubel, May 18 2019
(GAP) Filtered([1..100], n-> not (Factorial(n)+1) mod (2*n+1)=0) # G. C. Greubel, May 18 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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EXTENSIONS
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STATUS
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approved
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