cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A049596 Primes p such that x^9 = 2 has a solution mod p.

Original entry on oeis.org

2, 3, 5, 11, 17, 23, 29, 31, 41, 43, 47, 53, 59, 71, 83, 89, 101, 107, 113, 127, 131, 137, 149, 157, 167, 173, 179, 191, 197, 223, 227, 229, 233, 239, 251, 257, 263, 269, 277, 281, 283, 293, 311, 317, 347, 353, 359, 383, 389, 397, 401, 419, 431, 439, 443, 449
Offset: 1

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Keywords

Comments

Coincides with sequence of "primes p such that x^27 = 2 has a solution mod p" for first 339 terms, then diverges.
Complement of A059262 relative to A000040. - Vincenzo Librandi, Sep 15 2012

Examples

			0^9 == 2 (mod 2). 2^9 == 2 (mod 3). 2^9 == 2 (mod 5). 6^9 == 2 (mod 11). 2^9 == 2 (mod 17). 9^9 == 2 (mod 23). 11^9 == 2 (mod 29). 16^9 == 2 (mod 31). 20^9 == 2 (mod 41). 26^9 == 2 (mod 43). - _R. J. Mathar_, Jul 20 2025
		

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(500) | exists(t){x : x in ResidueClassRing(p) | x^9 eq 2}]; // Vincenzo Librandi, Sep 15 2012
  • Mathematica
    ok[p_]:= Reduce[Mod[x^9 - 2, p] == 0, x, Integers] =!= False; Select[Prime[Range[100]], ok] (* Vincenzo Librandi, Sep 15 2012 *)

A059354 Primes p such that x^27 = 2 has no solution mod p, but x^9 = 2 has a solution mod p.

Original entry on oeis.org

3943, 11287, 12853, 14149, 17659, 20143, 21061, 21277, 23059, 23599, 25759, 26407, 26731, 29863, 32833, 33751, 35803, 37747, 38287, 39367, 39799, 46441, 47737, 47791, 57781, 59887, 61291, 62047, 63127, 65557, 68311, 71443, 73063, 78301
Offset: 1

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Author

Klaus Brockhaus, Jan 27 2001

Keywords

Crossrefs

Programs

  • Magma
    [ p: p in PrimesUpTo(80000) | exists(t){x: x in ResidueClassRing(p) | x^9 eq 2} and forall(t){x : x in ResidueClassRing(p) | x^27 ne 2} ]; // Klaus Brockhaus, Dec 05 2008
  • Mathematica
    Select[Prime[Range[PrimePi[80000]]], !MemberQ[PowerMod[Range[#], 27, #], Mod[2, #]] && MemberQ[PowerMod[Range[#], 9, #], Mod[2, #]] &] (* Vincenzo Librandi, Sep 21 2013 *)

Extensions

a(25)-a(34) from Klaus Brockhaus, Dec 05 2008

A070180 Primes p such that x^3 = 2 has a solution mod p, but x^(3^2) = 2 has no solution mod p.

Original entry on oeis.org

109, 307, 433, 739, 811, 919, 1423, 1459, 1999, 2017, 2143, 2179, 2251, 2287, 2341, 2791, 2917, 2953, 3061, 3259, 3331, 3457, 3889, 4177, 4339, 4519, 4663, 5113, 5167, 5419, 5437, 5653, 6301, 6427, 6661, 6679, 6967, 7723, 7741, 8011, 8389, 8713
Offset: 1

Views

Author

Klaus Brockhaus, Apr 29 2002

Keywords

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(10000) | not exists{x: x in ResidueClassRing(p) | x^9 eq 2} and exists{x: x in ResidueClassRing(p) | x^3 eq 2}]; // Vincenzo Librandi, Sep 21 2012
    
  • PARI
    forprime(p=2,8800,x=0; while(x
    				
  • PARI
    ok(p, r, k1, k2)={
        if (  Mod(r,p)^((p-1)/gcd(k1,p-1))!=1, return(0) );
        if (  Mod(r,p)^((p-1)/gcd(k2,p-1))==1, return(0) );
        return(1);
    }
    forprime(p=2,10^4, if (ok(p,2,3,3^2),print1(p,", ")));
    /* Joerg Arndt, Sep 21 2012 */
Showing 1-3 of 3 results.