Special neighbor primes: Difference between revisions
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;Task:Let ('''p<sub>1</sub>''', '''p<sub>2</sub>''') are neighbour primes. Find and show here in base ten if '''p<sub>1</sub>+ p<sub>2</sub> -1''' is prime |
;Task:Let ('''p<sub>1</sub>''', '''p<sub>2</sub>''') are neighbour primes. Find and show here in base ten if '''p<sub>1</sub>+ p<sub>2</sub> -1''' is prime, where '''p<sub>1</sub>, p<sub>2</sub> < 100'''. |
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Revision as of 04:58, 6 August 2021
Special neighbor primes is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
- Task
- Let (p1, p2) are neighbour primes. Find and show here in base ten if p1+ p2 -1 is prime, where p1, p2 < 100.
Ring
<lang ring> load "stdlib.ring"
see "working..." + nl see "Special neighbour primes are:" + nl row = 0 oldPrime = 2
for n = 3 to 100
if isprime(n) and isprime(oldPrime) sum = oldPrime + n - 1 if isprime(sum) row++ see "" + oldPrime + "," + n + " => " + sum + nl ok oldPrime = n ok
next
see "Found " + row + " special neighbour primes" see "done..." + nl </lang>
- Output:
working... Special twin primes are: 3,5 => 7 5,7 => 11 7,11 => 17 11,13 => 23 13,17 => 29 19,23 => 41 29,31 => 59 31,37 => 67 41,43 => 83 43,47 => 89 61,67 => 127 67,71 => 137 73,79 => 151 Found 13 special twin primesdone...