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.

A258081 Values of k in A071580.

Original entry on oeis.org

1, 1, 1, 1, 2, 10, 12, 10, 21, 25, 70, 670, 239, 2115, 586, 1619, 26800, 2505, 99019, 40903, 285641, 67166, 1852765
Offset: 1

Views

Author

Andrew R. Booker, May 19 2015

Keywords

Comments

The first 23 terms were found using gwnum, and the first 22 have been independently checked using gmp.

Links

Crossrefs

Cf. A061092, A072532, A113334.

Programs

  • PARI
    terms=12; p=2; for(n=2, terms, q=p+1; while(!ispseudoprime(q), q=q+p); print1(q\p,", "); p=p*q) \\ Serge Batalov, May 19 2015

A090475 Beginning with 2, a(n+1) is the least prime == -1 (mod Product_{i=1..n} a(i) ).

Original entry on oeis.org

2, 3, 5, 29, 2609, 2269829, 20608503836279, 3397683442959574948323216959, 42930190020276065993287927763424183433168916230440704129, 1192530198055712826264639739575734950954723597893286538562918677849035900498296709057759892487138176511608345909
Offset: 1

Views

Author

Amarnath Murthy, Dec 02 2003

Keywords

Crossrefs

Cf. A090474, A090476, A071580, A258081.

Programs

  • PARI
    terms=12; p=2; print1("2, "); for(n=2, terms, q=p-1; while(!ispseudoprime(q), q=q+p); print1(q, ", "); p=p*q) \\ Serge Batalov, May 22 2015

Extensions

Corrected and extended by David Wasserman, Nov 16 2005

A263539 Smallest odd prime of the form k*a(n-1)*a(n-2)*...*a(1) + 2.

Original entry on oeis.org

3, 5, 17, 257, 65537, 73014444017, 7839866227890585600377, 90965983657404652017189201081165598949585237, 59265532390032181385721703100931439246761487956490653915298719426194939212611074425177277
Offset: 1

Views

Author

Jeppe Stig Nielsen, Oct 20 2015

Keywords

Comments

Infinite sequence of primes which coincides with Fermat primes, a(n) = A019434(n-1), only for n <= 5.
For the k values, see A263540.

Crossrefs

Cf. A071580, A090475, A263540, A019434.

Programs

  • PARI
    terms=12; p=1; for(n=1, terms, q=p+2; while(!ispseudoprime(q), q+=2*p); print1(q, ", "); p*=q)

A359340 The primes associated with A339174.

Original entry on oeis.org

2, 3, 7, 43, 3613, 65250781, 38318979202732621, 8810065002836730577256726488782121, 6131762382982476362788562753503495060507087787406616806191258317645081
Offset: 1

Views

Author

Jeppe Stig Nielsen, Dec 27 2022

Keywords

Comments

a(1)=2; for n > 0, a(n+1) is the first prime of the form k*(a(n) - 1)*a(n) + 1. It exists by Dirichlet's theorem on arithmetic progressions.
It is simple to reconstruct a(n) from A339174, which has the more compact representation.

Crossrefs

Cf. A061092, A071580, A339174.

Programs

  • PARI
    p=2; k=1; print1(p, ", "); while(1, runningP=k*(p-1)*p+1; if(ispseudoprime(runningP), k=1; p=runningP; print1(p, ", ") , k++))
Showing 1-4 of 4 results.

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

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