A008920 Let j = | i - i_written_backwards |, k = j + j_written_backwards; then k is in this sequence.

0, 18, 99, 198, 261, 342, 423, 504, 585, 666, 747, 828, 909, 1089, 1170, 1251, 1332, 1413, 1494, 1575, 1656, 1737, 1818, 1881, 1998, 2772, 2871, 3663, 3762, 4554, 4653, 5445, 5544, 6336, 6435, 7227, 7326, 8118, 8217, 9009, 9108, 9999, 10890, 10989, 11781

Offset

1,2

Comments

There were originally some terms missing from this sequence, for example 909 generated from 101001. It seems likely to me that Conway only checked generators up to 100000. It's possible to prove that there are now no missing terms of the sequence by noting that if an n-digit number is not a palindrome then the difference between it and its reversal is at least 9*10^(n/2 - 1). - Oscar Cunningham, Sep 10 2021

References

J. H. Conway, personal communication.

Links

Oscar Cunningham, Table of n, a(n) for n = 1..30484

Crossrefs

Cf. A004086, A335978.

Sequence in context: A177371 A044269 A044650 * A221911 A263999 A087638

Adjacent sequences: A008917 A008918 A008919 * A008921 A008922 A008923

Keyword

nonn,base

Author

N. J. A. Sloane and J. H. Conway

Extensions

Offset 1 and missing terms added by Oscar Cunningham, Sep 10 2021

Status

approved