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 1-5 of 5 results.

A088762 Numbers n such that (2n-1, 2n+3) is a cousin prime pair.

Original entry on oeis.org

2, 4, 7, 10, 19, 22, 34, 40, 49, 52, 55, 64, 82, 97, 112, 115, 139, 154, 157, 175, 190, 199, 220, 229, 232, 244, 250, 307, 322, 337, 370, 379, 385, 412, 427, 430, 439, 442, 454, 469, 484, 505, 544, 547, 607, 640, 649, 652, 712, 715, 724, 742, 745, 775, 784, 790
Offset: 1

Views

Author

Ray Chandler, Oct 26 2003

Keywords

Links

Crossrefs

Essentially the same as A111981.
Cf. A087679, A088764, A088766, A088768, A088770.

Programs

Formula

a(n) = (A087679(n)-1)/2 = (A023200(n)+1)/2 = (A046132(n)-3)/2.

A087682 Numbers n such that n + 8 and n - 8 are both prime.

Original entry on oeis.org

11, 15, 21, 39, 45, 51, 75, 81, 105, 159, 165, 171, 189, 219, 231, 249, 285, 339, 345, 375, 381, 441, 471, 495, 549, 555, 579, 585, 609, 639, 651, 669, 735, 765, 819, 831, 945, 975, 1005, 1041, 1095, 1101, 1179, 1209, 1221, 1299, 1311, 1431, 1479, 1491
Offset: 1

Views

Author

Zak Seidov, Sep 27 2003

Keywords

Links

Crossrefs

Cf. A014574, A087678-A087683, A087695-A087697, A088768.

Programs

Extensions

More terms from Ray Chandler, Oct 26 2003

A088764 a(n) = (A087680(n)-1)/2.

Original entry on oeis.org

3, 4, 7, 13, 16, 28, 31, 37, 46, 52, 67, 76, 88, 97, 118, 133, 136, 181, 196, 202, 217, 226, 241, 247, 283, 286, 298, 301, 328, 343, 352, 361, 373, 382, 412, 457, 466, 493, 508, 517, 532, 556, 583, 598, 613, 616, 643, 646, 661, 688, 721, 727, 742, 763, 781, 787
Offset: 1

Views

Author

Ray Chandler, Oct 26 2003

Keywords

Links

Crossrefs

Cf. A087680, A088762, A088766, A088768, A088770.

Programs

  • Magma
    [(n-1)/2: n in [2..2000] |IsPrime(n+4) and IsPrime(n-4)]; // Vincenzo Librandi, May 19 2017
  • Mathematica
    f[n_]:=PrimeQ[n - 4] && PrimeQ[n + 4]; lst={}; Do[If[f[n], AppendTo[lst, (n - 1) / 2]], {n, 3, 7!, 2}]; lst (* Vincenzo Librandi, May 19 2017 *)
(#-1)/2&/@(Select[Prime[Range[250]],PrimeQ[#+8]&]+4) (* Harvey P. Dale, May 21 2023 *)

A088766 a(n) = (A087681(n)-1)/2.

Original entry on oeis.org

5, 6, 8, 11, 12, 17, 18, 23, 26, 32, 33, 36, 38, 47, 51, 53, 66, 71, 72, 78, 86, 92, 93, 102, 108, 116, 117, 122, 128, 131, 137, 138, 143, 171, 176, 186, 197, 201, 207, 212, 213, 218, 227, 236, 242, 246, 248, 257, 281, 296, 303, 306, 312, 318, 323, 326, 333, 366
Offset: 1

Views

Author

Ray Chandler, Oct 26 2003

Keywords

Comments

Numbers k such that 2*k + 1 - 6 and 2*k + 1 + 6 are sexy primes. [Jonathan Vos Post, Feb 14 2011]

Examples

			1002 is in the sequence because 2*1002 + 1 - 6 = 1999 is prime, and 2*1002 + 1 + 6 = 2011 is prime.

Links

Crossrefs

Cf. A023201, A046117, A087681, A088762, A088764, A088765, A088768, A088770, A186243.

Programs

  • Magma
    [n-1: n in [3..400] |IsPrime(2*n+5) and IsPrime(2*n-7)]; // Vincenzo Librandi, May 20 2017
  • Mathematica
    Select[Range[3, 1000], PrimeQ[2 # + 5] && PrimeQ[2 # - 7] &] - 1 (* Vincenzo Librandi, May 20 2017 *)

Formula

{k such that 2*k + 1 - 6 is in A023201} = {k such that 2*k + 1 + 6 is in A046117}.

A088770 a(n) = (A087683(n)-1)/2.

Original entry on oeis.org

6, 10, 13, 16, 25, 28, 31, 34, 46, 49, 58, 70, 73, 91, 94, 100, 130, 133, 136, 151, 160, 163, 178, 181, 184, 199, 205, 214, 226, 238, 244, 256, 265, 283, 298, 301, 304, 325, 331, 364, 409, 424, 433, 436, 448, 478, 490, 493, 511, 514, 520, 529, 553, 556, 559
Offset: 1

Views

Author

Ray Chandler, Oct 26 2003

Keywords

Links

Crossrefs

Cf. A087683, A088762, A088764, A088766, A088768.

Programs

  • Magma
    [(n-1)/2: n in [8..2000] |IsPrime(n+10) and IsPrime(n-10)]; // Vincenzo Librandi, May 22 2017
  • Mathematica
    Rest[f[n_]:=PrimeQ[n - 10] && PrimeQ[n + 10]; lst={}; Do[If[f[n], AppendTo[lst, (n - 1) / 2]], {n, 5, 7!, 2}]; lst] (* Vincenzo Librandi, May 22 2017 *)
Showing 1-5 of 5 results.

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

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