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A097386
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Numbers n such that (largest digit of n)^(smallest digit of n) + n is prime.
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2
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1, 10, 21, 30, 32, 40, 43, 60, 61, 65, 70, 81, 92, 100, 102, 106, 108, 130, 150, 152, 161, 172, 174, 180, 183, 185, 190, 210, 221, 232, 240, 250, 252, 270, 280, 283, 285, 292, 298, 306, 310, 322, 330, 354, 361, 372, 376, 381, 394, 400, 408, 420, 423, 430, 460
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internal format)
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OFFSET
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1,2
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COMMENTS
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No term ends in 9. Conjecture: Let f(x)=(largest digit of x)^(smallest digit of x) + x. There are infinitely many positive integers n such that f(n) and f(n+1) are both prime; see A097387.
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LINKS
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Table of n, a(n) for n=1..55.
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EXAMPLE
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1272 is in the sequence because 7^2 + 1272 = 1321, a prime.
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MATHEMATICA
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okQ[n_]:=Module[{idn=IntegerDigits[n]}, PrimeQ[Max[idn]^Min[idn]+n]]
Select[Range[500], okQ] (* Harvey P. Dale, Dec 11 2010 *)
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CROSSREFS
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Cf. A054054, A054055, A097385, A097387.
Sequence in context: A087598 A242287 A165403 * A108685 A108686 A078209
Adjacent sequences: A097383 A097384 A097385 * A097387 A097388 A097389
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jason Earls, Aug 18 2004
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EXTENSIONS
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Corrected by T. D. Noe, Oct 25 2006
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STATUS
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approved
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