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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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15
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101, 1100011, 11100000111, 111100000001111, 1111100000000011111, 11111100000000000111111, 111111100000000000001111111, 1111111100000000000000011111111, 11111111100000000000000000111111111
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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
| a(n)={(10^n-1)*[1+10^(3n-1)]}/9, with n>=1 [From Paolo P. Lava (paoloplava(AT)gmail.com), Nov 26 2008]
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EXAMPLE
| n ........... a(n)
1 ........... 101
2 ......... 1100011
3 ....... 11100000111
4 ..... 111100000001111
5 ... 1111100000000011111
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CROSSREFS
| 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 * A082521 A138826 A138720
Adjacent sequences: A138117 A138118 A138119 * A138121 A138122 A138123
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KEYWORD
| base,easy,nonn
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), Apr 06 2008
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