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Search: id:A087094
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| A087094 |
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a(n) = smallest k such that (10^k-1)/9 == 0 mod prime(n)^2, or 0 if no such k exists. |
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4
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| 0, 9, 0, 42, 22, 78, 272, 342, 506, 812, 465, 111, 205, 903, 2162, 689, 3422, 3660, 2211, 2485, 584, 1027, 3403, 3916, 9312, 404, 3502, 5671, 11772, 12656, 5334, 17030, 1096, 6394, 22052, 11325, 12246, 13203, 27722, 7439, 31862, 32580, 18145, 37056, 19306
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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For a given a(n)>0, all of the values of k such that (10^k-1)/9=0 mod prime(n)^2 is given by the sequence a(n)*A000027, i.e. integral multiples of a(n). For example, for n=2, prime(2)=3, a(n)=9, the set of values of k for which (10^k-1)/9=0 mod 3^2 is 9*A000027=9,18,27,36,45,...
The union of the collection of sequences formed from the nonzero terms of a(n)*A000027, gives the values of k for which (10^k-1)/9 is not square-free, see A046412. All of terms of the sequence a(n) are integer multiples of prime(n) for primes <1000 except for a(93)=486 where prime(93)=487. Conjecture: there are no 0 terms after a(3).
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EXAMPLE
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a(2)=9 since 9 is least value of k for which (10^k-1)/9=0 mod 3^2.
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CROSSREFS
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Cf. A000040, A000042, A046412, A084006, A084007.
Sequence in context: A076262 A167301 A013534 this_sequence A013535 A167319 A057403
Adjacent sequences: A087091 A087092 A087093 this_sequence A087095 A087096 A087097
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KEYWORD
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nonn
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AUTHOR
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Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 10 2003
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