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 1-1 of 1 results.

A331667 Numbers m with a divisor d such that tau(d)^d = m.

Original entry on oeis.org

1, 4, 19683, 65536, 2176782336, 101559956668416, 7958661109946400884391936
Offset: 1

Views

Author

Jaroslav Krizek, Feb 28 2020

Keywords

Comments

Corresponding values of divisors d and tau(d) are 1, 2, 9, 8, 12, 18, 32, ..., and 1, 2, 3, 4, 6, 6, 6, ..., respectively.
a(8) = 2^144*3^72 = 12^72 is too large to be included in Data. - Giovanni Resta, Feb 28 2020

Examples

			19683 is a term because 3^9 = 19683; 9 divides 19683, tau(9) = 3.

Crossrefs

Cf. A236284 (tau(n)^n).
Cf. A000005, A332646.

Programs

  • Magma
    [n: n in [1..100000] | #[d: d in Divisors(n) | NumberOfDivisors(d)^d eq n] ge 1]
  • Mathematica
    seqQ[n_] := AnyTrue[Divisors[n], DivisorSigma[0, #]^# == n &]; Select[Range[70000], seqQ] (* Amiram Eldar, Feb 28 2020 *)
  • PARI
    isok(m) = fordiv(m, d, if (numdiv(d)^d == m, return (1));); \\ Michel Marcus, Mar 07 2020

Extensions

More terms from Giovanni Resta, Feb 28 2020
Showing 1-1 of 1 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.