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 1-4 of 4 results.

A103805 Primes p such that 2*p - 27 and 2*p + 27 are positive primes.

Original entry on oeis.org

17, 23, 37, 43, 83, 103, 127, 197, 257, 307, 313, 317, 337, 373, 457, 673, 677, 727, 733, 797, 863, 887, 937, 953, 1013, 1063, 1283, 1303, 1597, 1667, 1693, 1777, 1783, 1987, 1997, 2053, 2063, 2267, 2297, 2393, 2473, 2543, 2707, 2777, 2833, 2837
Offset: 1

Views

Author

Zak Seidov, Feb 16 2005

Keywords

Links

Crossrefs

Cf. A103802, A103803, A103804.

Programs

  • Magma
    [p: p in PrimesUpTo(3000) | IsPrime(2*p-27) and IsPrime(2*p+27)]; // Vincenzo Librandi, Nov 16 2010
  • Mathematica
    Select[Range[17,2000], PrimeQ[ # ] && PrimeQ[2# + 27] && PrimeQ[2# - 27] &]
Select[Prime[Range[5,500]],And@@PrimeQ[2#+{27,-27}]&] (* Harvey P. Dale, Jul 06 2013 *)

Extensions

More terms from Vincenzo Librandi, Mar 17 2010

A103806 Primes p such that 2p - 33 and 2p + 33 are both primes.

Original entry on oeis.org

2, 5, 7, 13, 19, 23, 37, 47, 53, 67, 73, 103, 137, 157, 163, 173, 193, 227, 233, 277, 313, 347, 353, 397, 443, 457, 613, 733, 863, 877, 983, 1087, 1153, 1213, 1327, 1447, 1493, 1733, 1747, 1787, 1867, 2053, 2063, 2153, 2237, 2377, 2383, 2503, 2557, 2657, 2683
Offset: 1

Views

Author

Zak Seidov, Feb 16 2005

Keywords

Comments

If, e.g., -29 is not prime (Mathematica considers -prime as prime), then the first four terms should be omitted.

Links

Crossrefs

Cf. A103802, A103803, A103804, A103805.

Programs

  • Magma
    [p: p in PrimesUpTo(3000)| IsPrime(2*p+33) and IsPrime(2*p-33) ]; // Vincenzo Librandi, Jan 28 2011
  • Mathematica
    Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 33] && PrimeQ[2# - 33] &]
Select[Prime[Range[400]],AllTrue[2#+{33,-33},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Sep 10 2016 *)

Formula

p, 2p-33 and 2p+33 all are primes.

A103804 Primes p such that both 2p +/- 21 are primes.

Original entry on oeis.org

13, 19, 29, 31, 41, 59, 79, 89, 101, 109, 131, 179, 211, 239, 241, 271, 311, 331, 349, 409, 421, 449, 499, 509, 521, 541, 601, 619, 701, 751, 821, 839, 881, 1009, 1091, 1181, 1201, 1319, 1321, 1399, 1429, 1459, 1489, 1531, 1571, 1619, 1801, 1949, 1951
Offset: 1

Views

Author

Zak Seidov, Feb 16 2005

Keywords

Crossrefs

Cf. A103802, A103803.

Programs

  • Mathematica
    Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]
Select[Prime[Range[4,500]],And@@PrimeQ[2#+{21,-21}]&] (* Harvey P. Dale, Dec 18 2012 *)

Formula

p, 2p-21 and 2p+21 all are positive primes.

A171518 Primes p such that 3*p-+8 are primes.

Original entry on oeis.org

5, 7, 13, 17, 53, 73, 83, 113, 127, 157, 193, 223, 277, 347, 367, 433, 613, 647, 673, 743, 797, 907, 937, 1117, 1217, 1373, 1427, 1483, 1543, 1597, 1637, 1667, 1877, 1933, 2027, 2237, 2297, 2447, 2647, 2687, 2843, 3083, 3137, 3613, 3797, 4073, 4463, 4483
Offset: 1

Views

Author

Vladimir Joseph Stephan Orlovsky, Dec 10 2009

Keywords

Examples

			5 is in the sequence since 3*5-8=7 and 3*5+8=23 are primes.

Links

Crossrefs

Cf. A000040, A005382, A005384, A023204-A023207, A063908-A063912, A103803, A124098, A125272, A171517

Programs

  • Mathematica
    Select[Prime[Range[7! ]],PrimeQ[3*#-8]&&PrimeQ[3*#+8]&]
Select[Prime[Range[700]],AllTrue[3#+{8,-8},PrimeQ]&] (* Harvey P. Dale, Feb 10 2025 *)
Showing 1-4 of 4 results.

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

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