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

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

1,1

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

Links

Harry J. Smith and Charles R Greathouse IV, Table of n, a(n) for n = 1..651 (first 70 terms from Smith)

Prog

(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

Crossrefs

Subsequence of A008364.

Cf. A000010, A000203, A065818, A065819, A062699, A065822, A274535(5*sigma(n)).

Sequence in context: A139198 A004800 A322065 * A233198 A358162 A049654

Adjacent sequences: A065820 A065821 A065822 * A065824 A065825 A065826

Keyword

nonn

Author

Labos Elemer, Nov 23 2001

Extensions

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

Status

approved