[seqfan] Re: More palindromes by concatenation

[Eric Angelini]

Hello SeqFans,
this is now here, thanks to Lars Blomberg.
http://www.cetteadressecomportecinquantesignes.com/MorePalindromes.htm
Best,
É.

> Hello SeqFans,
Start S with 1 and always extend S with the smallest integer a(n) producing a palindrome string of concatenated digits involving at least the first digit of a(n) and the last digit of a(n-1); I guess S starts:

S=1,10,11,12,2,13,3,14,4,15,5,16,6,17,7,18,8,19,9,29,20,21,22,23,24,25,26,27,28,38,30,31,32,33,34,35,36,37,39,49,40,41,42,43,44,45,46,47,48,58,50,51,52,53,54,55,56,57,59,69,60,61,62,63,64,65,66,67,68,78,70,71,72,73,74,75,76,77,79,89,80,81,82,83,84,85,86,87,88,98,90,91,92,93,94,95,96,97,99,119,100,101,102,120,103,130,104,140,105,106,160,107,170,...

Example:
S=1,10,... as 10 is the smallest integer not already in S producing a palindrome: [11];
S=1,10,11,... as 11 produces [101];
S=1,10,11,12,... as 12 prod. [11];
S=1,10,11,12,2,... as 2 prod. [22];
S=1,10,11,12,2,13,... as 13 --> [1221], etc.

Remember: the palindrome must contain at least the leftmost digit of the new term and the rightmost digit of the previous one.