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Search: id:A111477
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| A111477 |
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a(1) = 11, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime. |
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4
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| 11, 19, 19, 37, 21, 71, 101, 39, 61, 87, 227, 63, 437, 153, 1363, 117, 363, 861, 609, 249, 23, 1077, 3123, 771, 3717, 633, 279, 1119, 927, 107, 3843, 4313, 1729, 627, 12541, 2403, 4083, 1239, 2227, 6441, 3819, 3983, 5631, 2303, 2971, 19217, 3633, 5109, 14413, 913
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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11,111919,111919191919,... are all prime.
111919191919 = one copy of 11, two copies of 19, three copies of 19.
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CROSSREFS
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Cf. A111471, A111472, A111473, A111474, A111475, A111478.
Sequence in context: A066950 A162011 A123248 this_sequence A004750 A065126 A145059
Adjacent sequences: A111474 A111475 A111476 this_sequence A111478 A111479 A111480
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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), Aug 05 2005
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EXTENSIONS
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a(4)-a(8) from Stefan Steinerberger (hansibal(AT)hotmail.com), Nov 17 2005
Extended by Max Alekseyev (maxale(AT)gmail.com), May 20 2009
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