(12C+) how many primes between two numbers
06-30-2019, 11:30 PM (This post was last modified: 06-30-2019 11:41 PM by Don Shepherd.)
Post: #1
 Don Shepherd Senior Member Posts: 713 Joined: Dec 2013
(12C+) how many primes between two numbers
Here is a cute little program for the 12c+ that will tell you the number of prime numbers between two numbers you specify. It takes a rather brute force approach, which is why I recommend it for the 12c+ and not the slower 12c.

It also uses the N financial register as a flag. If you set N=0, it will just tell you the number of primes between the two numbers you specify. If you set N to anything else, it will pause and show you (briefly) each prime that it finds, and give you the total primes at the end. I think this is a neat and easy way to use N as a flag.

To use the program, set N to 0 or non-zero depending upon whether you want to see each prime, then enter your range in X and Y (lower point in Y, upper point in X), then press R/S and be amazed. It works best if your range is under 1000 or 2000, because although the 12c+ is fast, it is still brute force.

Code:
 01 sto 2 02 x<->y 03 sto 1 04 0 05 sto 3 06 rcl 1 07 2 08 / 09 frac 10 x=0 11 goto 13 12 goto 15 13 1 14 sto+1 15 3 16 sto 0 17 rcl 1 18 sqrt 19 sto 6 20 rcl 1 21 rcl 0 22 / 23 frac 24 x=0 25 goto 39 26 2 27 sto+0 28 rcl 6 29 rcl 0 30 x<=y 31 goto 20 32 rcl n 33 x=0 34 goto 37 35 rcl 1 36 pse 37 1 38 sto+3 39 2 40 sto+1 41 rcl 2 42 rcl 1 43 x<=y 44 goto 15 45 rcl 3
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 Messages In This Thread (12C+) how many primes between two numbers - Don Shepherd - 06-30-2019 11:30 PM RE: (12C+) how many primes between two numbers - Gamo - 08-22-2019, 06:48 AM

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