View Full Version : Ten prime numbers describing an arithmetic sequence
K Sengupta
Feb17-09, 01:41 PM
Ten distinct prime numbers, each less than 3000, when arranged in increasing order of magnitude describe an arithmetic sequence.
What are these ten prime numbers?
Rogerio
Feb17-09, 02:35 PM
But the sum of the prime numbers p and p+d are even, but also equal to the prime number p+3d, a contradiction.
Why p+p+d = p+3d ???
jimmysnyder
Feb17-09, 02:52 PM
199 + n * 210 (where n = 0, 1, 2, ..., 9) are all primes.
I found this by brute force. Here's an easy question. This is a run of length 10. There are two runs of length 9. What are they?
davee123
Feb17-09, 05:58 PM
Here's an easy question. This is a run of length 10. There are two runs of length 9. What are they?
Are you implying that there are more runs of 9 besides the 2 included within your run of 10?
But while we're doing brute force:
There's only 1 run of length 10 within all the primes up to a max of 3000. But how high do you have to push the max before you find another run of 10? How many runs of 10 are there with all the primes below 1 million?
DaveE
Georgepowell
Feb17-09, 06:07 PM
They are on the form p,p+d,p+2d..., where p is an odd prime and d is a positive integer. But the sum of the prime numbers p and p+d are even, but also equal to the prime number p+3d, a contradiction.
p + p + d =/= p + d+d+d simple mistake
jimmysnyder
Feb18-09, 08:05 AM
Are you implying that there are more runs of 9 besides the 2 included within your run of 10?
This isn't jeopardy. Pose your answer in the form of an answer.
davee123
Feb18-09, 01:11 PM
This isn't jeopardy. Pose your answer in the form of an answer.
Ok, just checking.
And another brute forcer: what's the longest run of arithmetically sequenced primes below 1 million?
DaveE
davee123
Feb24-09, 04:47 PM
So, just so I don't leave these questions without answers:
There's only 1 run of length 10 within all the primes up to a max of 3000. But how high do you have to push the max before you find another run of 10?
53813
How many runs of 10 are there with all the primes below 1 million?
144
What's the longest run of arithmetically sequenced primes below 1 million?
The longest run is 15 primes
DaveE
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