[seqfan] Fun with palindromic runs

[Eric Angelini]

Hello SeqFans,
from our "Silly Sequences' Storage", here is S:

S is a permutation of the Naturals (by definition) and
S self-describes its own palindromic runs' sizes of 
concatenated terms:

S=1,2,12,3,4,5,6,7,8,9,10,11,13,14,13111019876543,15,16,151,17,18,19,18171,20,21,22,23,2221202,...

-Indeed, the first palindromic run has size 1 --> this is '1'
-concatenating the next 2 terms produces a palindrome --> 2+12 = '212'
-concatenating the next 12 terms produces a palindrome: 
    3+4+5+6+7+8+9+10+11+13+14+13111019876543 = 
    '34567891011131413111019876543'
-concatenating the next 3 terms produces a palindrome: --> 15+16+151='1516151'
-concatenating the next 4 terms produces a palindrome: --> 17+18+19+18171='17181918171'
etc.

In building this sequence "always use the smallest available
integer not leading to a contradiction"...
Best,
É.