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[ February 3, 2002 ]
Find more palindromic pseudoprimes to base 2.

The first few palindromes
that are pseudoprime to base 2 are

101101
129921
1837381
127665878878566721
1037998220228997301
?
A068445

Can you extend the list with a few more terms ?
Beware, it might be a tougher job than it appears at first...

[ email dd. March 10, 2002 ]
Shyam Sunder Gupta cracked the fourth palindromic psp(2).
The number is 127665878878566721.
( 7 * 11 * 19 * 41 * 73 * 137 * 271 * 577 * 1361 )
This is in fact not only psp(2) but psp in all bases
i.e. it is a Carmichael Number
and this is the second palindromic  Carmichael number.
Interestingly the sum of digits of this number is 100.

[ October 19, 2002 ]
Shyam Sunder Gupta (email) cracked the fifth palindromic psp(2).
The number is 1037998220228997301.
( 41 * 101 * 211 * 251 * 757 * 1321 * 4733 )
Unfortunately it is not a strong pseudoprime(base 2).

Anyone interested in finding the sixth palindromic psp(2)
and/or the third palindromic Carmichael number ?


A000124 Prime Curios! Prime Puzzle
Wikipedia 124 Le nombre 124














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