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.

A356021 Positive numbers k such that, for any consecutive prime numbers p, q <= A006530(n), the p-adic and q-adic valuations of n are different.

Original entry on oeis.org

1, 2, 3, 4, 8, 9, 10, 12, 16, 18, 20, 21, 24, 27, 32, 40, 45, 48, 50, 54, 63, 64, 72, 75, 80, 81, 84, 90, 96, 100, 108, 110, 126, 128, 135, 144, 147, 160, 162, 168, 189, 192, 200, 220, 243, 250, 256, 270, 273, 288, 300, 320, 324, 336, 350, 360, 375, 378, 384
Offset: 1

Views

Author

Rémy Sigrist, Jul 23 2022

Keywords

Comments

Equivalently, these are fixed points of A356014.
This sequence is infinite as it contains A066205 and A066206.
If m is a term, then m^k is a term (for any k >= 0).

Crossrefs

Programs

  • PARI
    is(n) = { my (v=-1); forprime (p=2, oo, if (n==1, return (1), v==v=valuation(n,p), return (0), n\=p^v)) }