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A111475
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a(1) = 7, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.
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5
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7, 3, 1, 1, 1, 1, 129, 123, 97, 559, 781, 459, 253, 183, 413, 417, 657, 77, 437, 1439, 667, 1281, 3379, 979, 2763, 1953, 103, 10083, 5103, 291, 1311, 2199, 1159, 501, 5931, 483, 6171, 16301, 1781, 1229, 9519, 607, 5113, 2641, 1441, 8511, 9023, 363, 4001, 15261
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OFFSET
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1,1
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LINKS
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EXAMPLE
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7,733,733111,... are all prime.
733111 = one copy of 7, two copies of 3, three copies of 1.
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CROSSREFS
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KEYWORD
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base,hard,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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