mersenneforum.org  

Go Back   mersenneforum.org > Fun Stuff > Puzzles

Reply
 
Thread Tools
Old 2020-10-11, 18:10   #1
R2357
 
"Ruben"
Oct 2020
Nederland

2·19 Posts
Smile A little puzzle

Hello,
I thought I would give the forum a little puzzle that I made :)


Here is the puzzle :

What do the numbers 3, 4, 5, 9, 10 and 15 have in common?

Have fun solving :)
R2357 is offline   Reply With Quote
Old 2020-10-11, 18:37   #2
Viliam Furik
 
Jul 2018
Martin, Slovakia

1000010002 Posts
Default

OEIS sequence A217040? Bases b in which the increasing concatenation of all primes smaller than b forms a prime number.
Viliam Furik is offline   Reply With Quote
Old 2020-10-11, 18:55   #3
R2357
 
"Ruben"
Oct 2020
Nederland

2×19 Posts
Default

Well done!
R2357 is offline   Reply With Quote
Old 2020-10-11, 19:37   #4
Viliam Furik
 
Jul 2018
Martin, Slovakia

10816 Posts
Default

Quote:
Originally Posted by R2357 View Post
Well done!
Well, that was quick... Another one, please!
Viliam Furik is offline   Reply With Quote
Old 2020-10-11, 20:22   #5
Uncwilly
6809 > 6502
 
Uncwilly's Avatar
 
"""""""""""""""""""
Aug 2003
101×103 Posts

213548 Posts
Default

3, 4, 9, 8, 9, 9, 8, 9, 9, 8...

Last fiddled with by Uncwilly on 2020-10-11 at 21:50
Uncwilly is online now   Reply With Quote
Old 2020-10-11, 20:25   #6
sweety439
 
sweety439's Avatar
 
Nov 2016

22×3×211 Posts
Default

Quote:
Originally Posted by R2357 View Post
Hello,
I thought I would give the forum a little puzzle that I made :)


Here is the puzzle :

What do the numbers 3, 4, 5, 9, 10 and 15 have in common?

Have fun solving :)
They are all divisors of 360 (the number of degrees in a turn)
sweety439 is offline   Reply With Quote
Old 2020-10-11, 20:43   #7
Viliam Furik
 
Jul 2018
Martin, Slovakia

23×3×11 Posts
Default

Quote:
Originally Posted by Uncwilly View Post
3, 4, 9, 8, 9, 8...
I will gues OEIS A239384 - (Decimal expansion of the probability of a normal-error variable exceeding the mean by more than three standard deviations), however it's most probably not correct, since you now know I search in OEIS.
Viliam Furik is offline   Reply With Quote
Old 2020-10-11, 21:49   #8
Uncwilly
6809 > 6502
 
Uncwilly's Avatar
 
"""""""""""""""""""
Aug 2003
101×103 Posts

894010 Posts
Default

Quote:
Originally Posted by Viliam Furik View Post
I will gues OEIS A239384
That sequence starts with 1. I made an error. I have now corrected the sequence.
Uncwilly is online now   Reply With Quote
Old 2020-10-11, 23:32   #9
a1call
 
a1call's Avatar
 
"Rashid Naimi"
Oct 2015
Remote to Here/There

3×11×59 Posts
Default

oeis won't help you for this one:


4, 11,14, 17
a1call is offline   Reply With Quote
Old 2020-10-12, 00:41   #10
a1call
 
a1call's Avatar
 
"Rashid Naimi"
Oct 2015
Remote to Here/There

3·11·59 Posts
Default

Quote:
Originally Posted by a1call View Post
oeis won't help you for this one:


4, 11,14, 17
Hint: They are all consecutive integers n for which f1(n) and f2(n) are Twin-Prime-Pairs.
a1call is offline   Reply With Quote
Old 2020-10-12, 05:58   #11
R2357
 
"Ruben"
Oct 2020
Nederland

2·19 Posts
Smile Another riddle :)

Quote:
Originally Posted by Viliam Furik View Post
Well, that was quick... Another one, please!

Here goes, what do pi and the prime number sequence have in common (apart from pi's usage in the prime counting function and in the Gapcoin symbol)?
R2357 is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
More than just a puzzle storm5510 Puzzles 5 2020-10-07 14:14
Some puzzle Harrywill Puzzles 4 2017-05-03 05:10
A well-known puzzle... mart_r Puzzles 31 2009-04-09 22:51
Dot puzzle nibble4bits Puzzles 37 2006-02-27 09:35
now HERE'S a puzzle. Orgasmic Troll Puzzles 6 2005-12-08 07:19

All times are UTC. The time now is 02:55.

Fri Dec 4 02:55:01 UTC 2020 up 23:06, 0 users, load averages: 2.20, 2.04, 1.72

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.