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Search: id:A157677
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| A157677 |
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Prime numbers p such that p + (product of digits) is also prime. |
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+0
1
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| 23, 29, 61, 67, 83, 101, 103, 107, 109, 163, 233, 239, 283, 293, 307, 347, 349, 401, 409, 431, 439, 443, 449, 499, 503, 509, 563, 569, 601, 607, 613, 617, 619, 653, 659, 677, 683, 701, 709, 743, 809, 907, 929, 941, 1009, 1013, 1019, 1021, 1031, 1033, 1039
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If p contains a zero, then a(p) is trivial.
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FORMULA
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a(p) = p + DigitProduct(p)
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EXAMPLE
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83 is prime, and a(83) = 83 + (8)(3) = 89 which is also prime. 103 is prime, and a(103) = 103 + (1)(0)(3) = 103 which is prime.
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MAPLE
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a := proc (n) local nn: nn := convert(ithprime(n), base, 10): if isprime(ithprime(n)+product(nn[j], j = 1 .. nops(nn))) = true then ithprime(n) else end if end proc: seq(a(n), n = 1 .. 180); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 08 2009]
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CROSSREFS
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Adjacent sequences: A157674 A157675 A157676 this_sequence A157678 A157679 A157680
Sequence in context: A097436 A063980 A046124 this_sequence A092518 A110584 A115396
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KEYWORD
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nonn,base
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AUTHOR
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Kyle D. Balliet (kdballie(AT)bloomu.edu), Mar 04 2009
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 08 2009
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