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.

A109275 Complement of A109274 and A109273.

Original entry on oeis.org

12, 42, 46, 60, 66, 72, 82, 102, 106, 108, 126, 150, 162, 166, 172, 178, 180, 190, 192, 222, 226, 240, 262, 268, 276, 282, 292, 312, 346, 348, 358, 372, 388, 396, 408, 420, 432, 448, 456, 460, 462, 466, 486, 502, 508, 520, 522, 540, 568, 570, 586, 612, 630
Offset: 1

Views

Author

Zak Seidov, Jun 25 2005

Keywords

Crossrefs

Cf. A109273, A109274.

A109274 Numbers k such that k+1 is prime, 2k+1 composite.

Original entry on oeis.org

4, 10, 12, 16, 22, 28, 40, 42, 46, 52, 58, 60, 66, 70, 72, 82, 88, 100, 102, 106, 108, 112, 126, 130, 136, 148, 150, 162, 166, 172, 178, 180, 190, 192, 196, 222, 226, 232, 238, 240, 250, 256, 262, 268, 276, 280, 282, 292, 310, 312, 316, 346, 348, 352, 358
Offset: 1

Views

Author

Zak Seidov, Jun 25 2005

Keywords

Comments

Includes all terms from A109273.

Crossrefs

Cf. A109273, A109275, A307390.

Programs

  • Mathematica
    Select[Range[358],PrimeQ[#+1]&&CompositeQ[2#+1]&] (* James C. McMahon, Mar 05 2024 *)
  • PARI
    isok(n) = isprime(n+1) && !isprime(2*n+1); \\ Michel Marcus, Oct 06 2013

Formula

a(n) = A307390(n) - 1. - Bhavik Mehta, Aug 14 2024

Extensions

Corrected by Michel Marcus, Oct 06 2013
Showing 1-2 of 2 results.

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

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