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Find out (Posted on 2012-01-08) Difficulty: 3 of 5
How many k-digit palindromes are prime?
Please solve for k=1,2,3, ... 9.

No Solution Yet Submitted by Ady TZIDON    
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re: computer solution--something bad happened at the unasked-for k=11 Comment 2 of 2 |
(In reply to computer solution by Charlie)

Sloane shows 42042 for k=11, rather than my 7871, so something went wrong. Apparently UBASIC returns a zero for the prmdiv function if its largest prime divisor is bigger than a certain value, such as in:

?prmdiv(98765432137)
 0

C'est l'informatique.


  Posted by Charlie on 2012-01-08 13:29:35
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