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Search: id:A050683
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| A050683 |
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Number of palindromes of length n. |
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+0
13
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| 9, 9, 90, 90, 900, 900, 9000, 9000, 90000, 90000, 900000, 900000, 9000000, 9000000, 90000000, 90000000, 900000000, 900000000, 9000000000, 9000000000, 90000000000, 90000000000, 900000000000, 900000000000, 9000000000000
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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In general the number of base k palindromes with n digits is (k-1)*k^floor[(n-1)/2].
This sequence does not count 0 as palindrome with 1 digit, see A070252=(10,9,90,90...) for the variant which does. [From M. F. Hasler (MHasler(AT)univ-ag.fr), Nov 16 2008]
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LINKS
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Dr. Math, More info 1.
Dr. Math, More info 2.
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FORMULA
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a(n) = 9*10^floor[(n-1)/2]
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PROGRAM
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(PARI) A050683(n)=9*10^((n-1)\2) [From M. F. Hasler (MHasler(AT)univ-ag.fr), Nov 16 2008]
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CROSSREFS
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Cf. A002113, A050250, A050251, A070252, A070199. Cf. A016116 for numbers of binary palindromes, A016115 for prime palindromes.
Sequence in context: A112296 A038299 A165427 this_sequence A092548 A121389 A065242
Adjacent sequences: A050680 A050681 A050682 this_sequence A050684 A050685 A050686
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KEYWORD
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nonn,easy,base,nice
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Aug 15 1999.
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EXTENSIONS
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Additional comments from Henry Bottomley (se16(AT)btinternet.com), Aug 14 2000
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