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 A008920 Let j = | i - i_written_backwards |, k = j + j_written_backwards; then k is in this sequence. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified September 11 14:49 EDT 2024. Contains 375836 sequences. (Running on oeis4.)