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Lychrel number
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==Other bases== In [[Binary number|base 2]], 10110 (22 in decimal) has been proven to be a Lychrel number, since after 4 steps it reaches 10110100, after 8 steps it reaches 1011101000, after 12 steps it reaches 101111010000, and in general after 4''n'' steps it reaches a number consisting of 10, followed by ''n'' + 1 ones, followed by 01, followed by ''n'' + 1 zeros. This number obviously cannot be a palindrome, and none of the other numbers in the sequence are palindromes. Lychrel numbers have been proven to exist in the following bases: 11, 17, 20, 26, and all powers of 2.<ref>See comment section in {{OEIS2C|id=A060382}}</ref><ref>{{cite web |title= Digit Reversal Sums Leading to Palindromes |url=http://www.mathpages.com/home/kmath004/kmath004.htm}}</ref><ref>{{cite web |title=Letter from David Seal |url=http://www.mathpages.com/home/dseal.htm |access-date=2017-03-08 |archive-url=https://web.archive.org/web/20130530003702/http://mathpages.com/home/dseal.HTM |archive-date=2013-05-30 |url-status=dead }}</ref> No base contains any Lychrel numbers smaller than the base. In fact, in any given base ''b'', no single-digit number takes more than two iterations to form a palindrome. For ''b'' > 4, if ''k'' < ''b''/2 then ''k'' becomes palindromic after one iteration: ''k'' + ''k'' = 2''k'', which is single-digit in base ''b'' (and thus a palindrome). If ''k'' > ''b''/2, ''k'' becomes palindromic after two iterations. The smallest number in each base which could possibly be a Lychrel number are {{OEIS|id=A060382}}: {|class="wikitable" |- !''b'' !Smallest possible Lychrel number in base ''b''<br />written in base ''b'' (base 10) |- |2 |10110<ref>Proven to be a Lychrel Number, see {{OEIS|id=A060382}}</ref> (22) |- |3 |10211 (103) |- |4 |10202 (290) |- |5 |10313 (708) |- |6 |4555 (1079) |- |7 |10513 (2656) |- |8 |1775 (1021) |- |9 |728 (593) |- |10 |196 (196) |- |11 |83A (1011) |- |12 |179 (237) |- |13 |12CA (2701) |- |14 |1BB (361) |- |15 |1EC (447) |- |16 |19D (413) |- |17 |B6G (3297) |- |18 |1AF (519) |- |19 |HI (341) |- |20 |IJ (379) |- |21 |1CI (711) |- |22 |KL (461) |- |23 |LM (505) |- |24 |MN (551) |- |25 |1FM (1022) |- |26 |OP (649) |- |27 |PQ (701) |- |28 |QR (755) |- |29 |RS (811) |- |30 |ST (869) |- |31 |TU (929) |- |32 |UV (991) |- |33 |VW (1055) |- |34 |1IV (1799) |- |35 |1JW (1922) |- |36 |YZ (1259) |}
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