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Search: id:A088115
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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
1
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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
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(26) = 9719 as 989,899 both 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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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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Sequence in context: A095927 A137981 A110351 this_sequence A048986 A093712 A035514
Adjacent sequences: A088112 A088113 A088114 this_sequence A088116 A088117 A088118
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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 25 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jul 25 2005
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