Wikipedia:Reference desk/Archives/Mathematics/2021 January 27

= January 27 =

Are these already a class of numbers?
I've recently been messing around with a set of numbers I call the Mcook Numbers. However, I'm not sure if these have already been studied or named yet.

The numbers are 42, 62, 63, 82, 84, 93, and 822. They are categorized by this:

If you divide both of the digits (for example, 4/2), you will have a quotient that is a natural number above 1. Are these already a thing? — Preceding unsigned comment added by Eridian314 (talk • contribs) 02:23, 27 January 2021 (UTC)


 * The On-Line Encyclopedia of Integer Sequences has no entry matching your numbers (even if I omit the last). —Tamfang (talk) 02:55, 27 January 2021 (UTC)
 * These also satisfy your definition: 21, 31, 41, 51, 61, 71, 81, 91. You haven't given a definition for numbers with more than two digits and I cannot guess why you list 822 next. Maybe you meant 842. A096106 is more general: "Numbers such that every digit is a multiple of the digit to its right." PrimeHunter (talk) 08:22, 27 January 2021 (UTC)


 * In sequence A096106, the quotient of a pair of successive digits may be 1 (as it is in 822 for the last pair). If these quotients must all be above 1, as stated in the definition, 822 is out and only a finite number of terms are left: the 1-digit natural numbers below 10, and 22 larger numbers: 21, 31, 41, 42, 51, 61, 62, 63, 71, 81, 82, 84, 91, 93, 421, 621, 631, 821, 841, 842, 931, 8421. This sequence is not listed in OEIS, and I see no particularly interesting properties. --Lambiam 09:26, 27 January 2021 (UTC)

Thanks. I consider ones with divisors of 1 to be "trivial".. And 822 would be 8/2/2, or a quotient of 2. My bad. I should've explained it better. — Preceding unsigned comment added by Eridian314 (talk • contribs) 13:45, 27 January 2021 (UTC)

Bad Format
I was reading the article Four-dimensional space and saw a very bad formatted section which was added a week ago by User:Komarom31. Could someone look at the content? Greetings Bigbossfarin (talk) 21:57, 27 January 2021 (UTC)
 * Reverted: Special:Diff/1003208543. --CiaPan (talk) 22:43, 27 January 2021 (UTC)