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.

A178700 Lonely primes between two consecutive nontrivial powers.

Original entry on oeis.org

127, 223, 251, 64007, 1295033, 2535525373, 542939080319
Offset: 1

Views

Author

Marot Alain (marot.alain(AT)orange.fr), Jun 05 2010

Keywords

Comments

While the number of perfect powers < n is ~ sqrt(n) and the number of primes < n is ~ n/log(n), this does not preclude more terms from existing, but it does make it very unlikely. [Robert G. Wilson v, Jun 10 2010]

Examples

			5^3 < 127 < 2^7;
6^3 < 223 < 15^2;
3^5 < 251 < 2^8;
40^3 < 64007 < 253^2;
109^3 < 1295033 < 1138^2.
From _Carlos Rivera_, Nov 26 2013: (Start)
50354^2 < 2535525373 < 76^5;
8158^3 < 542939080319 < 736844^2. (End)
		

Programs

  • Mathematica
    nextPerfectPower[n_] := Block[{k = n + 1}, While[ GCD @@ Last /@ FactorInteger@k == 1, k++ ]; k]; a = 1; b = 3; lst = {}; While[a < 15 10^8, If[ PrimePi@b == 1 + PrimePi@a, p = NextPrime@a; AppendTo[lst, p]; Print@p]; a = b; b = nextPerfectPower@b]; lst (* Robert G. Wilson v, Jun 10 2010 *)

Extensions

First 5 terms checked by Robert G. Wilson v, Jun 10 2010
a(6)-a(7) from Carlos Rivera, Nov 26 2013