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.

User: Kellen Shenton

Kellen Shenton's wiki page.

Kellen Shenton has authored 3 sequences.

A379380 Prime numbers p such that (2*p)# - p# + 1 is prime, where p# = A034386(p).

Original entry on oeis.org

1, 2, 5, 17, 103, 113, 193, 277, 3671, 9419, 12671, 30809, 34439, 83833, 89227, 106103, 107101, 175303, 398903
Offset: 1

Author

Kellen Shenton, Dec 21 2024

Keywords

Examples

			For p = 17: the product of the primes from 2 to p*2 is 2*3*5*7*11*13*17*19*23*29*31 = 200560490130, and the product of the primes from 2 to p is 2*3*5*7*11*13*17 = 510510.  200560490130 - 510510 + 1 = 200559979621, a prime number.
		

Crossrefs

A357280 Smallest m such that m^k-2 and m^k+2 are prime for k=1..n.

Original entry on oeis.org

5, 9, 102795, 559838181, 27336417022509
Offset: 1

Author

Kellen Shenton, Sep 24 2022

Keywords

Examples

			a(3) = 102795 because:
for k = 1; 102795^1-2 = 102793 and 102795^1+2 = 102797, both of which are prime, and
for k = 2; 102795^2-2 = 10566812023 and 102795^2+2 = 10566812027, both of which are prime, and
for k = 3; 102795^3-2 = 1086215442109873 and 102795^3+2 = 1086215442109877, both of which are prime, and
102795 is the smallest number with this property.
		

Crossrefs

Programs

  • PARI
    isok(m,n) = for (k=1, n, if(!isprime(m^k-2) || !isprime(m^k+2), return(0));); return(1);
    a(n) = my(m=1); while(!isok(m, n), m++); m; \\ Michel Marcus, Nov 14 2022

A352736 a(n) is the smallest b >= 2 such that 1 + Sum_{k=0..n} b^(2^k) is prime, or 1 if no such b exists.

Original entry on oeis.org

2, 2, 2, 1, 6, 3, 448, 107, 104, 1, 4556, 1, 24124, 121209, 368, 177817, 48330, 1
Offset: 0

Author

Kellen Shenton, Mar 30 2022

Keywords

Comments

Polynomial factorizations exist for n=3,9,11,17,27 and may exist for other n > 27.
For those n for which a proven factorization exists, b=1 results in a prime of the form n+2.

Examples

			a(6)=448 because 448 is the smallest number b such that 1 + Sum_{k=0..6} b^(2^k) is prime.
		

Extensions

a(16)-a(17) from Kellen Shenton, May 08 2022