[ *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 ?