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.

A280005 Least prime p such that p^n + 1 is the product of n distinct primes.

Original entry on oeis.org

2, 3, 13, 43, 73, 47, 457, 1697, 109, 8161, 10429, 13183, 30089, 66569, 5281
Offset: 1

Views

Author

Altug Alkan, Feb 24 2017

Keywords

Comments

Corresponding values of p^n + 1 are 3, 10, 2198, 3418802, 2073071594, 10779215330, 4163067000501310394, ...
a(16) <= 206874667. - Daniel Suteu, Dec 09 2022

Examples

			a(2) = 3; 3^2 + 1 = 2 * 5.
a(3) = 13; 13^3 + 1 = 2 * 7 * 157.
a(4) = 43; 43^4 + 1 = 2 * 17 * 193 * 521.
		

Crossrefs

Programs

  • PARI
    a(n) = my(p=2); while (!issquarefree(p^n+1) || omega(p^n+1) != n, p = nextprime(p+1)); p;

A363585 Least prime p such that p^n + 6 is the product of n distinct primes.

Original entry on oeis.org

5, 2, 23, 127, 71, 353, 1279, 3851, 3049, 18913, 47129, 352073, 696809
Offset: 1

Views

Author

J.W.L. (Jan) Eerland, Jun 10 2023

Keywords

Comments

Corresponding values of p^n + 6 are 11, 10, 12173, 260144647, 1804229357, 1934854145598535, 5598785270206921122565, ...
Upper bounds for the next terms are a(12) <= 352073, a(13) <= 696809, a(14) <= 1496423. - Hugo Pfoertner, Jun 11 2023

Examples

			a(1) = 5; 5^1 + 6 = 11.
a(2) = 2; 2^2 + 6 = 2 * 5.
a(3) = 23; 23^3 + 6 = 7 * 37 * 47.
a(4) = 127; 127^4 + 6 = 7 * 131 * 367 * 773.
		

Crossrefs

Programs

  • Mathematica
    Table[b=6;y[a_]:=FactorInteger[Prime[a]^n+b];k=1;Monitor[Parallelize[While[True,If[And[Length[y[k]]==n,Count[Flatten[y[k]],1]==n],Break[]];k++];k],k]//Prime,{n,1,10}]
  • PARI
    a(n) = forprime(p=2, , my(f=factor(p^n + 6)); if (issquarefree(f) && (omega(f) == n), return(p)));

Extensions

a(11) from Hugo Pfoertner, Jun 11 2023
a(12) from J.W.L. (Jan) Eerland, Jan 07 2024
a(13) from Hugo Pfoertner, confirmed by Daniel Suteu, Feb 10 2024

A368162 a(n) is the smallest number k > 0 such that bigomega(k^n + 1) = n.

Original entry on oeis.org

1, 3, 3, 43, 7, 32, 23, 643, 17, 207, 251, 3255, 255, 1568, 107
Offset: 1

Views

Author

Daniel Suteu, Dec 14 2023

Keywords

Comments

a(16) <= 206874667; a(17) = 4095; a(18) = 6272; a(21) = 1151.

Examples

			a(5) = 7 is the smallest number of the set {k(i)} = {7, 14, 24, 26, 46, 51, ...} where k(i)^5 + 1 has exactly 5 prime factors counted with multiplicity.
		

Crossrefs

Programs

  • PARI
    a(n) = my(k=1); while (bigomega(k^n+1) != n, k++); k;

A379768 a(n) is the smallest prime p such that omega(p^n + 1) = n.

Original entry on oeis.org

2, 3, 5, 43, 17, 47, 151, 1697, 59, 2153, 521, 13183, 30089, 66569, 761
Offset: 1

Views

Author

Daniel Suteu, Jan 06 2025

Keywords

Comments

2*10^6 < a(16) <= 206874667; a(18) = 33577; a(20) <= 3258569.
A219018(n) <= a(n) <= A280005(n).

Examples

			a(3) = 5 is the smallest prime of the set {p(i)} = {5, 11, 13, 19, 23, ...} where omega(p(i)^3 + 1) = 3.
		

Crossrefs

Programs

  • Mathematica
    a[n_] := Module[{p = 2}, While[PrimeNu[p^n + 1] != n, p = NextPrime[p]]; p]; Print[Array[a, 11]]
  • PARI
    a(n) = forprime(p=2, oo, if(omega(p^n+1) == n, return(p)));
Showing 1-4 of 4 results.