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.

A112771 Semiprimes of the form 6n + 1.

Original entry on oeis.org

25, 49, 55, 85, 91, 115, 121, 133, 145, 169, 187, 205, 217, 235, 247, 253, 259, 265, 289, 295, 301, 319, 355, 361, 391, 403, 415, 427, 445, 451, 469, 481, 493, 505, 511, 517, 529, 535, 553, 559, 565, 583, 589, 649, 655, 667, 679, 685, 697, 703, 721, 745
Offset: 1

Views

Author

Jonathan Vos Post and Ray Chandler, Oct 15 2005

Keywords

Comments

Union of A108164 and A108166.
Subsequence of A091300. - Zak Seidov, Dec 28 2015

Programs

  • Magma
    IsSemiprime:=func; [s: n in [2..150] | IsSemiprime(s) where s is 6*n + 1]; // Vincenzo Librandi, Sep 22 2012
  • Mathematica
    Select[6 Range[0, 200] + 1, PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 22 2012 *)

Formula

a(n) = 6 * A112775(n) +1.