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.

A100858 Primes of the form (p - 1)! + p, p prime.

Original entry on oeis.org

3, 5, 29, 727, 3628811, 80658175170943878571660636856403766975289505440883277824000000000053
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 20 2004

Keywords

Comments

a(n) = A100856(k) = A100857(k) for some k.
Subset of A073309. - R. J. Mathar, Sep 02 2008
No more terms for p < 1250. - Vincenzo Librandi, Dec 26 2010

Crossrefs

Cf. A092791.

Programs

  • Magma
    [ a: p in PrimesUpTo(250) | IsPrime(a) where a is Factorial(p-1)+p ]; // Vincenzo Librandi, Dec 26 2010

A073308 Numbers k such that k! + k + 1 is prime.

Original entry on oeis.org

0, 1, 2, 4, 6, 10, 52, 6822, 30838
Offset: 1

Views

Author

Rick L. Shepherd, Jul 24 2002

Keywords

Comments

Clearly, for k>2, k != 2 (mod 3).
Often m! + 2, m! + 3, ..., m! + m is cited as a constructed sequence of m-1 consecutive composite numbers.
Except for 0, k+1 is prime. - Robert Israel, Jan 13 2015

References

  • J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 52, p. 20, Ellipses, Paris 2008.

Crossrefs

Cf. A073309 (corresponding primes), A002981 (n!+1 is prime), A073443 (n!-n-1 is prime), A092791.

Programs

  • Mathematica
    f[n_]:=n!+n+1; lst={};Do[p=f[n];If[PrimeQ[p],AppendTo[lst,n]],{n,0,2*5!}];lst (* Vladimir Joseph Stephan Orlovsky, Jul 02 2009 *)
  • PARI
    for(n=0,1960,if(isprime(n!+n+1),print1(n,",")))

Formula

a(n) = A092791(n) - 1. - Seiichi Manyama, Mar 19 2018

Extensions

a(8) from T. D. Noe, Jan 18 2008
a(9) from Seiichi Manyama (by using the data calculated by Giovanni Resta, May 04 2013), Mar 19 2018
Showing 1-2 of 2 results.

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

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