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.

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A307881 2*a(n) is the least number where k sets a new record such that 2*a(n)-k and 2*a(n)+k are prime and at least one of 2*a(n)-j and 2*a(n)+j is composite for all 0

Original entry on oeis.org

2, 4, 11, 23, 64, 68, 73, 119, 143, 172, 263, 452, 557, 868, 1238, 1579, 2864, 3533, 3637, 4252, 5171, 9263, 11282, 12388, 20036, 59119, 69332, 90131, 113783, 139283, 178612, 185714, 413788, 468059, 579932, 960707, 1879582, 2727031, 3266951, 3319868, 3591593
Offset: 1

Views

Author

Hugo Pfoertner, May 03 2019

Keywords

Comments

The corresponding records of k are given in A307882.

Links

Crossrefs

Cf. A065978, A293858, A307882, A325142.

Programs

  • PARI
    kmax=0; for(n=2,10^7,forstep(k=1,n,2,if(isprime(2*n-k)&&isprime(2*n+k),if(k>kmax,print1(n,", ");kmax=k);break(1))))

A307882 Records of the offset k in A307881, divided by 3.

Original entry on oeis.org

-1, 1, 3, 5, 7, 9, 11, 13, 15, 25, 29, 31, 39, 45, 61, 63, 75, 81, 85, 111, 123, 131, 151, 175, 207, 225, 241, 267, 301, 329, 335, 427, 435, 505, 539, 565, 611, 617, 665, 695, 739, 805, 843, 875, 1113, 1143, 1465, 1797, 1801, 1959, 2065, 2369, 2783
Offset: 1

Views

Author

Hugo Pfoertner, May 03 2019

Keywords

Comments

The divisibility of k by 3 of all terms after a(1) is conjectural. Offsets not divisible by 3 are given as -k instead of k/3.

Crossrefs

Cf. A065978, A293858, A307881, A325142.

Programs

  • PARI
    kmax=0; for(n=2,10^7,forstep(k=1,n,2,if(isprime(2*n-k)&&isprime(2*n+k),if(k>kmax,if(k%3!=0,print1(-k,", "),print1(k/3,", "));kmax=k);break(1))))
Showing 1-2 of 2 results.

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

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