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Search: id:A069871
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| A069871 |
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Numbers n that divide the concatenation of n-1 and n+1. |
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+0
6
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| 3, 9, 11, 33, 111, 333, 1111, 3333, 11111, 33333, 111111, 333333, 1111111, 3333333, 11111111, 33333333, 111111111, 333333333, 1111111111, 3333333333, 11111111111, 33333333333, 111111111111, 333333333333, 1111111111111
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OFFSET
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1,1
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COMMENT
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All the numbers of the form (10^k - 1)/3 and (10^k - 1)/9 are members.
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FORMULA
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a(1)=3, a(2)=9, a(2n-1)=(10^n-1)/9, a(2n)=(10^n-1)/3 - Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Feb 10 2003
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EXAMPLE
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3 belongs to this sequence as 3 divides 24, 11 belongs to this sequence as 11 divides 1012.
9 belongs to this sequence as 9 divides the concatenation of 8 and 10 i.e. 810.
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MATHEMATICA
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Select[ Range[10^8], Mod[ FromDigits[ Join[ IntegerDigits[ # - 1], IntegerDigits[ # + 1]]], # ] == 0 & ]
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CROSSREFS
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Cf. A069860, A069862, A088797, A088798.
Cf. A077192.
Sequence in context: A106305 A135365 A088877 this_sequence A061957 A136984 A073105
Adjacent sequences: A069868 A069869 A069870 this_sequence A069872 A069873 A069874
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 24 2002
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EXTENSIONS
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More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Feb 10 2003
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