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Search: id:A138826
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| A138826 |
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Concatenation of 2n-1 digits 1, n digits 0 and 2n-1 digits 1. |
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+0
12
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| 101, 11100111, 1111100011111, 111111100001111111, 11111111100000111111111, 1111111111100000011111111111, 111111111111100000001111111111111, 11111111111111100000000111111111111111
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n) has 5n-2 digits.
a(n) is also A147540(n) written in base 2. [From Omar E. Pol (info(AT)polprimos.com), Nov 08 2008]
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FORMULA
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a(n)=(10^(2n-1)-1+10^(5n-2)-10^(3n-1))/9. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 07 2008, corrected Nov 09 2008]
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EXAMPLE
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n ........... a(n)
1 ........... 101
2 ......... 11100111
3 ....... 1111100011111
4 ..... 111111100001111111
5 ... 11111111100000111111111
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CROSSREFS
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Cf. A138120, A138144, A138145, A138146, A138148, A138720, A138721, A138722.
Cf. A147540. [From Omar E. Pol (info(AT)polprimos.com), Nov 08 2008]
Sequence in context: A015041 A138120 A082521 this_sequence A138720 A006064 A015164
Adjacent sequences: A138823 A138824 A138825 this_sequence A138827 A138828 A138829
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KEYWORD
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base,easy,nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), Apr 06 2008
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EXTENSIONS
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Corrected typo in exponent of my formula. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 09 2008
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