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A088115
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a(n) = largest prime using least number of possible digits with a digit sum n, or 0 if no such number exists. E.g., if n > 9 and there are no two-digit primes with a given digit sum n then three-digit numbers are explored and so on.
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0
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0, 2, 3, 31, 5, 0, 7, 71, 0, 73, 83, 0, 67, 59, 0, 97, 89, 0, 991, 983, 0, 967, 977, 0, 997, 9791, 0, 9973, 9929, 0, 9967, 9887, 0, 99961, 8999, 0, 99991, 99929, 0, 99877, 99689, 0, 98899, 99989, 0, 999883, 999983, 0, 999769, 999959, 0, 999979, 989999, 0
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OFFSET
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1,2
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COMMENTS
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a(26) = 9719 as both 989 and 899 are composite. This is the first genuine case in which the number of digits used is more than floor(n/9) + 1 (after single-digit composite even numbers 4 and 8).
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LINKS
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EXAMPLE
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a(7) = 7.
a(8) = 71 as 8 is not a prime.
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CROSSREFS
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KEYWORD
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base,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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