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User: Romeo Mestrovic

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A198245 Euler primes: Primes p that divide E(p - 3), where E(k) is the k-th Euler number.

Original entry on oeis.org

149, 241, 2946901, 16467631, 17613227, 327784727, 426369739, 1062232319
Offset: 1

Author

Romeo Mestrovic, Oct 22 2011

Keywords

Comments

Also called Vandiver primes. - N. J. A. Sloane, Sep 25 2023
See A196230 for another sequence of "Euler primes". - N. J. A. Sloane, May 29 2022
The even-indexed Euler numbers are A028296, the odd-indexed Euler numbers are all zero.
Numerous combinatorial congruences recently obtained by Z. W. Sun and by Z. H. Sun contain the Euler numbers E(p-3) with a prime p.
Only three primes less than 3 * 10^6 satisfy this condition (the current members of the sequence).
Such primes have been recently suggested by Z. W. Sun; namely, Sun found the first and the second such primes, 149 and 241, and used them to discover new congruences involving E(p - 3).
This is reported by Zhi Wei Sun on Feb 08 2010 and the third prime was found by Romeo Mestrovic (on Sep 26 2011).
Mestrovic (2012) computes that only three primes < 10^7 are in the sequence, but he conjectures that the sequence is infinite. - Jonathan Sondow, Dec 18 2012
If it exists, a(9) > 2 * 10^9. - Hiroaki Yamanouchi, Aug 06 2017
Hathi et al. give a(3) as 2124679 and claim that the terms 2124679, 16467631, 17613227 were reported in Cosgrave, Dilcher, 2013, but 2124679 does not appear in table 2 in that paper. How is 2124679 related to this sequence? Note that 2124679 is the second Wolstenholme prime (A088164). - Felix Fröhlich, Apr 27 2021

References

  • J. B. Cosgrave, A Mersenne-Wieferich Odyssey, Manuscript, May 2022. See Section 18.8.

Programs

  • Mathematica
    Select[Prime[Range[2, 200]], IntegerQ[EulerE[# - 3]/#] &] (* Alonso del Arte, Oct 31 2011 *)

Extensions

a(4)-a(8) from Hiroaki Yamanouchi, Aug 06 2017