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Re: How the primality of R19 was discovered

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  • djbroadhurst
    ... http://www.ams.org/journals/bull/1930-36-12/S0002-9904-1930-05077-6/S0002-9904-1930-05077-6.pdf Another application of the principle was made by Hoppe in
    Message 1 of 2 , Aug 14, 2013
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      --- In primenumbers@yahoogroups.com,
      "julienbenney" <jpbenney@...> wrote:

      > there is no clue as to the exact method by which Hoppe proved
      > R19 to be a prime

      http://www.ams.org/journals/bull/1930-36-12/S0002-9904-1930-05077-6/S0002-9904-1930-05077-6.pdf

      Another application of the principle was made by Hoppe in
      the investigation of (10^19¬ól)/9. Two proofs of the
      primality of this number were submitted by him to the London
      Mathematical Society. The first proof consisted in isolating
      an unbroken sequence of the 73 smallest prime residues, in
      fact all those <=761. He submitted this proof to Cole, who
      did not consider it sufficient. This seems to indicate that
      Cole had some doubt as to the rigor of his own method. It
      was probably Cole's reply that prompted Hoppe to give an
      independent proof of the primality of his number, as
      described in his second communication to the Society.

      http://plms.oxfordjournals.org/content/s2-17/1/1.1.extract

      leads to

      Thursday, December 6th, 1917.

      Lt.-Col. Cunningham and Dr. Western communicated a paper by
      Mr. 0. Hoppe, "Proof of the Primality of N = (1/9)*(10^19-1)."*

      * A further paper on this subject by Mr. 0. Hoppe was
      communicated on February 14th, 1918; and an Abstract
      containing the results of both papers will be found in the
      Records of that meeting.

      Thursday, February 14th, 1918.

      Lt.-Col. Cunningham and Dr. Western gave an account of a
      further investigation by Mr. 0. Hoppe* on "The Primality of
      (1/9)*(10^19 -1)."

      * See Records of Proceedings, December 6th, 1917.

      ABSTRACTS.

      "The Primality of (1/9)*(10^19-1)."

      Mr. Oscar Hoppe.

      *Mr. Oscar Hoppe's papers deal with the number
      N=(1/9)*(10^19-1) and contain a summary of the results of
      his calculations. He first employed the process for
      factorising large numbers contained in Prof. F. N. Cole's
      paper (Bulletin American Math. Soc., Ser. 2, Vol. 10, p.
      134). He thus proved that p is a quadratic residue of every
      factor of N, where p represents any prime, less than 761, of
      which N is a quadratic residue, those of the form 4n+3
      being taken with a minus sign.

      He then searched for possible prime factors of N up to a
      limit about 23*10^6, as follows. From the properties of such
      factors to moduli 19, 8, 3, 5, 7, 11, 13, every prime factor
      must be congruent to one of 360 residues (mod 2282280). All
      the possible factors of these forms were excluded by using
      the tests of the quadratic character (mods 17, 19, ..., 127).

      Finally, he searched for solutions of N=x^2-y^2, excluding
      possible values of x in a similar manner. The result was that
      no factors were discovered,and that therefore N is a prime.

      He also found that 3^(N-1) = 1 (mod N), which does not
      furnish a proof that N is prime, but confirms the accuracy
      of the other calculations.

      *This Abstract (prepared by Dr. Western) gives a summary of
      the results obtained in two papers communicated at the
      meetings on December 6th, 1917, and February 14th, 1918.

      David
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