A little puzzle

R2357 · 2020-10-11, 18:10

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 :)

Viliam Furik · 2020-10-11, 18:37

OEIS sequence A217040? Bases b in which the increasing concatenation of all primes smaller than b forms a prime number.

R2357 · 2020-10-11, 18:55

Well done!

Viliam Furik · 2020-10-11, 19:37

Quote:

Originally Posted by R2357

Well done!

Well, that was quick... Another one, please!

Uncwilly · 2020-10-11, 20:22

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

sweety439 · 2020-10-11, 20:25

Quote:

Originally Posted by R2357

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)

Viliam Furik · 2020-10-11, 20:43

Quote:

Originally Posted by Uncwilly

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.

Uncwilly · 2020-10-11, 21:49

Quote:

Originally Posted by Viliam Furik

I will gues OEIS A239384

That sequence starts with 1. I made an error. I have now corrected the sequence.

a1call · 2020-10-11, 23:32

oeis won't help you for this one:

4, 11,14, 17

a1call · 2020-10-12, 00:41

Quote:

Originally Posted by a1call

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.

R2357 · 2020-10-12, 05:58

Quote:

Originally Posted by Viliam Furik

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)?

2020-10-11, 18:10	#1
R2357 "Ruben" Oct 2020 Nederland 2·19 Posts	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 :)

2020-10-11, 20:22	#5
Uncwilly 6809 > 6502 """"""""""""""""""" Aug 2003 101×103 Posts 2²·3³·5·17 Posts	3, 4, 9, 8, 9, 9, 8, 9, 9, 8... Last fiddled with by Uncwilly on 2020-10-11 at 21:50

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2020-10-11, 18:37	#2
Viliam Furik "Viliam Furík" Jul 2018 Martin, Slovakia 325₁₀ Posts	OEIS sequence A217040? Bases b in which the increasing concatenation of all primes smaller than b forms a prime number.

2020-10-11, 18:55	#3
R2357 "Ruben" Oct 2020 Nederland 2×19 Posts	Well done!

2020-10-11, 23:32	#9
a1call "Rashid Naimi" Oct 2015 Remote to Here/There 3673₈ Posts	oeis won't help you for this one: 4, 11,14, 17