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 1-3 of 3 results.

A171517 Primes p such that 2*p+11 is prime.

Original entry on oeis.org

3, 13, 31, 43, 73, 109, 151, 163, 181, 193, 199, 211, 223, 283, 331, 349, 373, 379, 409, 421, 433, 463, 499, 541, 571, 601, 613, 619, 643, 709, 739, 769, 823, 829, 883, 991, 1009, 1021, 1039, 1051, 1063, 1129, 1213, 1231, 1291, 1303, 1423, 1453, 1471, 1549
Offset: 1

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Author

Keywords

Examples

			2*3+11=17, which is prime.
		

Crossrefs

Programs

  • Magma
    [p: p in PrimesUpTo(1600) | IsPrime(2*p+11)]; // Vincenzo Librandi, Apr 27 2014
  • Mathematica
    Select[Prime[Range[6! ]],PrimeQ[2*#+11]&]

A290838 a(n) = smallest prime p such that 2p - 2n + 1 is prime.

Original entry on oeis.org

2, 2, 3, 5, 5, 7, 7, 13, 11, 11, 11, 13, 13, 19, 17, 17, 17, 19, 19, 37, 23, 23, 23, 29, 29, 31, 29, 29, 29, 31, 31, 37, 37, 41, 37, 37, 37, 43, 41, 41, 41, 43, 43, 61, 47, 47, 47, 53, 53, 67, 53, 53, 53, 59, 59, 61, 59, 59, 59, 61, 61, 67, 67, 71, 67, 67, 67, 73
Offset: 0

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Author

XU Pingya, Aug 11 2017

Keywords

Comments

a(n) > n. - Iain Fox, Nov 13 2017

Crossrefs

Programs

  • Mathematica
    Table[j=0; found=False; While[!found,j++; found=PrimeQ[2Prime[j]-2n+1] && 2Prime[j]-2n+1>0]; Prime[j],{n,67}]
    (* Second program: *)
    Table[SelectFirst[Prime@ Range[n^2], And[# > 0, PrimeQ@ #] &[2 # - 2 n + 1] &], {n, 67}] (* Michael De Vlieger, Aug 14 2017 *)
  • PARI
    a(n) = {my(p=2); while(!isprime(2*p-2*n+1), p = nextprime(p+1)); p; } \\ Michel Marcus, Aug 12 2017
    
  • PARI
    a(n) = forprime(p=n+1, , if(isprime(2*p - 2*n + 1), return(p))) \\ Iain Fox, Nov 13 2017

Formula

a(-n) = A290839(n+1) - Iain Fox, Dec 14 2017

Extensions

a(0) prepended by Iain Fox, Dec 14 2017

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

Keywords

Examples

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

Crossrefs

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 1-3 of 3 results.