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Search: id:A154390
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| A154390 |
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Composites with largest digit = prime. |
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+0
1
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| 12, 15, 20, 21, 22, 25, 27, 30, 32, 33, 35, 45, 50, 51, 52, 54, 55, 57, 70, 72, 74, 75, 76, 77, 102, 105, 112, 115, 117, 120, 121, 122, 123, 125, 130, 132, 133, 135, 145, 147, 150, 152, 153, 154, 155, 170, 171, 172, 174, 175, 176, 177, 200, 201, 202, 203, 205, 207
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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12 is in sequence because it is composite and its largest digit (2) is prime. 15 is in sequence because it is composite and its largest digit (5) is prime. 20 os in sequence because it is composite and its largest digit (2) is prime.
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MAPLE
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a := proc (n) local nn; nn := convert(n, base, 10): if isprime(n) = false and isprime(max(seq(nn[i], i = 1 .. nops(nn)))) = true then n else end if end proc: seq(a(n), n = 1 .. 220); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 27 2009]
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CROSSREFS
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Cf. A000040, A002808.
Sequence in context: A115349 A163657 A117815 this_sequence A156683 A050696 A144266
Adjacent sequences: A154387 A154388 A154389 this_sequence A154391 A154392 A154393
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KEYWORD
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nonn,base
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 08 2009
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EXTENSIONS
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Corrected by Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 28 2009
Corrected (added 21) and extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 27 2009
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