Timeline for What is an example of a sequence which "thins out" and is finite?
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Dec 12, 2019 at 4:35 | audit | First posts | |||
| Dec 12, 2019 at 4:38 | |||||
| Nov 16, 2019 at 4:04 | comment | added | Draco18s no longer trusts SE | @ApollyssupportsMonica Edited, better? | |
| Nov 16, 2019 at 4:04 | history | edited | Draco18s no longer trusts SE | CC BY-SA 4.0 | added 39 characters in body |
| Nov 16, 2019 at 2:28 | comment | added | Apollys supports Monica | Please re-read my comment and/or your post more carefully. You wrote "That is, a number that when you remove the leftmost digit leaves a number that is still prime." | |
| Nov 16, 2019 at 1:19 | comment | added | Draco18s no longer trusts SE | @ApollyssupportsMonica "every suffix" and "repeatedly remove left most digit" are the same thing. Every suffix of ABCD are BCD, CD, and D. You get these suffixes by repeatedly removing the leftmost digit. You start with a prime and every result is also a prime (which also means that every suffix is itself in the sequence). | |
| Nov 16, 2019 at 0:10 | comment | added | Apollys supports Monica | The link you gave describes a very different definition than the one introduced in the second sentence of your post. "Left-truncatable primes: every suffix is prime and no digits are zero." | |
| Nov 14, 2019 at 21:42 | history | edited | Draco18s no longer trusts SE | CC BY-SA 4.0 | added 3 characters in body |
| Nov 14, 2019 at 14:25 | history | edited | Draco18s no longer trusts SE | CC BY-SA 4.0 | added 191 characters in body |
| Nov 14, 2019 at 14:25 | comment | added | Draco18s no longer trusts SE | See A132394 for the order in which they are generated (eg. 2, 3, 5, 7, (1||_) 13, (2||_) 23, (4||_) 43...) and A227916 for "primes that remain prime when the leftmost digit is removed" which is an infinite sequence, as it does not require that the new prime also be in the sequence. A024785 is recursive. | |
| Nov 14, 2019 at 14:17 | comment | added | Draco18s no longer trusts SE | @tomsmeding Feel free to try it for yourself. Notice that the largest term starts with a 3 (meaning the only other digits available for a same-length prime must either be a 1 or a 2). Unfortunately, 157686312646216567629137 is not prime (factors: 19, 103, 659, 46662713, and 2620280423) nor is 257686312646216567629137 (factors: 3, 61, 1427, 18731411, and 52680003487). You an try the larger digits yourself. Its not so much that there aren't other 24 digit primes, but that for it to be in the sequence, all substrings by removing n leftmost digits must be prime. | |
| Nov 14, 2019 at 12:47 | comment | added | tomsmeding | "as no non-zero digit added to the left results in a new prime" -- I believe you that the statement is true, but it doesn't follow directly from your parenthetical, does it? Conceivably, there could be another left-truncatable prime with the same number of digits, that can be extended. | |
| Nov 14, 2019 at 1:35 | review | First posts | |||
| Nov 14, 2019 at 1:37 | |||||
| Nov 14, 2019 at 1:31 | history | answered | Draco18s no longer trusts SE | CC BY-SA 4.0 |