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 1-2 of 2 results.

A028879 Numbers k such that k^2 - 6 is prime.

Original entry on oeis.org

3, 5, 7, 13, 17, 23, 25, 47, 53, 55, 65, 67, 73, 77, 83, 85, 97, 107, 113, 115, 125, 133, 143, 145, 155, 167, 187, 193, 197, 203, 205, 215, 235, 263, 275, 293, 317, 323, 325, 343, 355, 367, 373, 377, 383, 395, 415, 457, 463, 467, 475, 487, 503, 505, 533, 545
Offset: 1

Views

Author

Patrick De Geest

Keywords

Links

Programs

Formula

a(n) = sqrt(A028880(n)+6). - Zak Seidov, Mar 10 2015

A154619 Primes of the form (4k^2 + 4k - 5)/5.

Original entry on oeis.org

23, 71, 167, 191, 479, 743, 1583, 2039, 2927, 3863, 5711, 6551, 7919, 9767, 10487, 11423, 15791, 16703, 18119, 21647, 21911, 24359, 27527, 32159, 35111, 35447, 38543, 43991, 45887, 46271, 52223, 54287, 55967, 60719, 67511, 69383, 76631
Offset: 1

Views

Author

Vincenzo Librandi, Jan 16 2009

Keywords

Comments

The numbers k that generate integers of the form (4k^2 + 4k - 5)/5 are in A047208. The primes are generated by the subset k = 5, 9, 14, 15, 24, 30, ... of these. - R. J. Mathar, Jan 25 2009

Links

Crossrefs

Cf. A028880.

Programs

  • Maple
    a := proc (n) if type((4/5)*n^2+(4/5)*n-1, integer) = true and isprime((4/5)*n^2+(4/5)*n-1) = true then (4/5)*n^2+(4/5)*n-1 else end if end proc: seq(a(n), n = 1 .. 340); # Emeric Deutsch, Jan 21 2009
  • Mathematica
    Select[Table[(4n^2+4n-5)/5,{n,3,200}],PrimeQ] (* Vincenzo Librandi, Jul 23 2012 *)

Extensions

Definition corrected and more terms from R. J. Mathar and Omar E. Pol, Jan 24 2009
Extended by Emeric Deutsch, Jan 21 2009
Showing 1-2 of 2 results.

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

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