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Search: id:A111479
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| A111479 |
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a(n) = least positive number such that (2 Concat Concat_{k=0}^n Repeat(A045572(n), a(n))) is a prime. A045572 = odd numbers not divisible by 5. |
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2
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OFFSET
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0,1
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COMMENT
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Concat is the operator that concatenates two numbers as decimal strings, and Repeat returns the number obtained by concatenating the first argument to itself the second argument number of times.
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EXAMPLE
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21 is not a prime, but 211 is, so a(0)=2.
211,2113,21137777777 are all primes.
21137777777 is a prime obtained as 2 followed by two 1's, one 3, and seven 7's, so a(2) = 7.
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CROSSREFS
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Cf. A111471, A111472, A111473, A111474, A111475, A111477, A111478, A111480.
Sequence in context: A011134 A144749 A021463 this_sequence A141513 A102817 A026252
Adjacent sequences: A111476 A111477 A111478 this_sequence A111480 A111481 A111482
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KEYWORD
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base,more,nonn,less
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 05 2005
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EXTENSIONS
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Edited by Frank Adams-Watters (FrankTAW(AT)Netscape.net), Aug 29 2006.
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