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Search: id:A087571
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| A087571 |
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Smallest prime which has the form of the concatenation n, n-1, n-2, n-3, .., n-k for some k < n, or 0 if no such prime exists. |
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+0
1
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| 0, 2, 3, 43, 5, 0, 7, 0, 0, 109, 11, 0, 13, 0, 0, 0, 17, 0, 19, 0, 0, 2221, 23, 2423, 25242322212019181716151413, 0, 2726252423, 0, 29, 0, 31, 0, 0, 3433, 0, 0, 37, 0, 0, 0, 41, 4241, 43, 0, 0, 4645444342414039, 47, 4847464544434241, 0, 0, 5150494847
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(p) = p. Conjecture; There are infinitely many composite numbers n such that a(n) is nonzero.
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EXAMPLE
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a(10) = 109 a concatenation of 10 and 9.
a(6) = 0 as no number in the sequence 6,65,654,6543,65432,654321 is prime.
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CROSSREFS
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Sequence in context: A123993 A101821 A121475 this_sequence A126018 A051099 A062581
Adjacent sequences: A087568 A087569 A087570 this_sequence A087572 A087573 A087574
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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), Sep 16 2003
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EXTENSIONS
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Corrected and extended by Gabriel Cunningham (gcasey(AT)mit.edu), Sep 21 2003
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