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.

A065823 Numbers k such that 6*phi(k) = 5*sigma(k).

Original entry on oeis.org

11, 527, 923, 36859, 40549, 55309, 88519, 120139, 138301, 280579, 293501, 313807, 529789, 719927, 2458859, 4864117, 6191413, 6811243, 7297877, 8402663, 8624107, 9487477, 10475821, 12356441, 12940957, 13624717, 13971229, 14869033, 15293137
Offset: 1

Views

Author

Labos Elemer, Nov 23 2001

Keywords

Comments

Not all terms are squarefree: a(74) = 137640191 = 13^2 * 89 * 9151. - Charles R Greathouse IV, Nov 13 2015
Apart from the first term, no terms are divisible by 2, 3, 5, 7, or 11. - Charles R Greathouse IV, Nov 13 2015

Crossrefs

Subsequence of A008364.

Programs

  • PARI
    n=0; for (m=1, 10^9, if (6*eulerphi(m) == 5*sigma(m), write("b065823.txt", n++, " ", m); if (n==70, return))) \\ Harry J. Smith, Nov 01 2009
    
  • PARI
    is(n)=my(f=factor(n)); 6*eulerphi(f)==5*sigma(f) \\ Charles R Greathouse IV, Nov 13 2015

Extensions

Terms a(16)-a(29) from Harry J. Smith, Nov 01 2009