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A277371
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Positive integers k that divide 7^k + 3.
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3
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1, 2, 4, 5, 26, 205, 2404, 88171, 1785134, 2010899, 58796834, 639723359, 657788549, 2050134685, 4809019972, 6114530474, 11931055777, 1292089439947, 1294667166242, 4586221808305
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OFFSET
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1,2
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COMMENTS
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No other terms below 10^15. Some larger terms: 68363072121992414, 95409505835353571, 1579273736555455916822694118995172, 5481414795965035698701145369881812, 14905708205837180834697194210878924, 45415365018055454586462673640490785681840279, 147329898999183698422689397719859437775766016038732177717811807964. - Max Alekseyev, Oct 18 2016
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LINKS
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FORMULA
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A066438(a(n)) = a(n) - 3 for n > 2.
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EXAMPLE
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7^5 + 3 = 16810 = 5 * 3362, so 5 is a term.
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MATHEMATICA
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Select[Range[10000], Divisible[7^# + 3, #] &] (* Alonso del Arte, Oct 11 2016 *)
Join[{1, 2}, Select[Range[21*10^5], PowerMod[7, #, #]==#-3&]] (* The program generates the first 10 terms of the sequence. *) (* Harvey P. Dale, Sep 21 2022 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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