# Palindromic primes in base 16

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**Palindromic primes in base 16****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
- Find palindromic primes in base 16, where
**n < 500**

## Ring

<lang ring> load "stdlib.ring" see "working..." + nl see "Palindromic primes in base 16:" + nl row = 0 decList = 0:15 baseList = ["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"] limit = 500

for n = 1 to limit

hex = decimaltobase(n,16) if ispalindrome(hex) and isprime(n) see "" + hex + " " row = row + 1 if row%5 = 0 see nl ok ok

next

see nl + "Found " + row + " palindromic primes in base 16" + nl see "done..." + nl

func decimaltobase(nr,base)

binList = [] binary = 0 remainder = 1 while(nr != 0) remainder = nr % base ind = find(decList,remainder) rem = baseList[ind] add(binList,rem) nr = floor(nr/base) end binlist = reverse(binList) binList = list2str(binList) binList = substr(binList,nl,"") return binList

</lang>

- Output:

working... Palindromic primes in base 16: 2 3 5 7 B D 11 101 151 161 191 1B1 1C1 Found 13 palindromic primes in base 16 done...