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Search: id:A138120
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| A138120 |
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Concatenation of n digits 1, 2n-1 digits 0 and n digits 1. |
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+0
16
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| 101, 1100011, 11100000111, 111100000001111, 1111100000000011111, 11111100000000000111111, 111111100000000000001111111, 1111111100000000000000011111111, 11111111100000000000000000111111111
(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 4n-1 digits.
a(n) is also A147539(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^n-1)*[1+10^(3n-1)]}/9, with n>=1 [From Paolo P. Lava (ppl(AT)spl.at), Nov 26 2008]
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EXAMPLE
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n ........... a(n)
1 ........... 101
2 ......... 1100011
3 ....... 11100000111
4 ..... 111100000001111
5 ... 1111100000000011111
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CROSSREFS
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Cf. A138144, A138145, A138146, A138148, A138720, A138721, A138722, A138826.
Cf. A147539. [From Omar E. Pol (info(AT)polprimos.com), Nov 08 2008]
Sequence in context: A015078 A031982 A015041 this_sequence A082521 A138826 A138720
Adjacent sequences: A138117 A138118 A138119 this_sequence A138121 A138122 A138123
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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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