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.

Previous Showing 31-33 of 33 results.

A107771 Numbers n such that 2*n + 5 and 5*n + 2 are primes.

Original entry on oeis.org

0, 1, 3, 7, 9, 13, 19, 21, 27, 31, 33, 39, 51, 61, 63, 67, 73, 79, 93, 97, 109, 111, 117, 123, 129, 151, 171, 177, 181, 187, 189, 217, 219, 237, 243, 247, 259, 297, 313, 319, 321, 327, 339, 357, 369, 373, 403, 417, 427, 441, 453, 457, 471, 483, 489, 493, 523, 529
Offset: 1

Views

Author

Zak Seidov, Mar 31 2006

Keywords

Comments

Union of A089038 and A111223.
Except for the first, all terms == 1 or 3 (mod 6). - Robert Israel, Apr 02 2020

Links

Crossrefs

Cf. A089038, A111223.

Programs

  • Maple
    select(n -> isprime(2*n+5) and isprime(5*n+2), [0,seq(i,i=1..1000,2)]); # Robert Israel, Apr 02 2020
  • Mathematica
    Reap[Do[If[PrimeQ[2*n+5]&&PrimeQ[5*n+2],Sow[n]],{n,0,600}]][[2,1]]

A243811 Numbers k such that 2*k+3 and 2*k+5 are both prime.

Original entry on oeis.org

0, 1, 4, 7, 13, 19, 28, 34, 49, 52, 67, 73, 88, 94, 97, 112, 118, 133, 139, 154, 172, 208, 214, 229, 259, 283, 298, 307, 319, 328, 403, 409, 412, 427, 439, 508, 514, 523, 529, 544, 574, 613, 637, 643, 649, 658, 712, 724, 739, 742, 802, 808, 832, 847, 859, 892, 934
Offset: 1

Views

Author

Vincenzo Librandi, Jun 11 2014

Keywords

Links

Crossrefs

Cf. A040040, A067076, A089038.

Programs

  • Magma
    [n: n in [0..1000] | IsPrime(2*n+3) and IsPrime(2*n+5)];
  • Mathematica
    Select[Range[0, 1000], PrimeQ[2 # + 3] && PrimeQ[2 # + 5] &]

Formula

a(n) = A040040(n)-2.

A141544 Odd numbers k such that 2k+5 is a prime.

Original entry on oeis.org

1, 3, 7, 9, 13, 19, 21, 27, 31, 33, 37, 39, 49, 51, 61, 63, 67, 73, 79, 81, 87, 93, 97, 103, 109, 111, 117, 123, 129, 133, 139, 151, 153, 163, 171, 177, 181, 187, 189, 207, 213, 217, 219, 229, 231, 237, 241, 243, 247, 249, 259, 271, 279, 283, 291, 297, 301, 307
Offset: 1

Views

Author

Giovanni Teofilatto, Aug 16 2008

Keywords

Comments

Superset of A107771. The corresponding primes are given by deleting the first entry in A002145. - R. J. Mathar, Aug 18 2008

Crossrefs

Cf. A002145, A020498, A087915, A089038, A090670, A107771.

Programs

  • Maple
    a:=proc(n) if isprime(2*n+5) then n end if end proc: seq(a(2*n-1), n=1..170); # Emeric Deutsch, Aug 17 2008
  • Mathematica
    Select[Range[1,307,2],PrimeQ[2#+5]&] (* James C. McMahon, Jul 26 2025 *)

Formula

A089038 INTERSECT A005408. - R. J. Mathar, Aug 18 2008
a(n) = A087915(n+1) - 1 = A090670(n+1) - 4. - Giovanni Teofilatto, Sep 07 2008

Extensions

Extended by Emeric Deutsch, Aug 17 2008 and R. J. Mathar, Aug 18 2008
Previous Showing 31-33 of 33 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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