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A095976
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Numbers k such that (largest digit of k) + (largest digit of k+1) is prime.
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1
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1, 2, 3, 5, 6, 8, 10, 11, 12, 13, 15, 16, 18, 19, 22, 23, 25, 26, 28, 33, 35, 36, 38, 39, 45, 46, 48, 55, 56, 58, 66, 68, 78, 79, 88, 100, 101, 102, 103, 105, 106, 108, 110, 111, 112, 113, 115, 116, 118, 119, 122, 123, 125, 126, 128, 133, 135, 136, 138, 139, 145, 146
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listen;
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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 terms contain digit 9 before a non-9. - Robert Israel, May 20 2020
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LINKS
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EXAMPLE
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12348 is in the sequence because 8 (its largest digit) plus 9 (the largest digit of 12349) equals 17 (a prime).
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MAPLE
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N:= 500: # to get terms <= N
L:= map(t -> max(convert(t, base, 10)), [$1..N+1]):
LL:= L[1..-2]+L[2..-1]:
select(t -> member(LL[t], {2, 3, 5, 7, 11, 13, 17}), [$1..N]); # Robert Israel, May 20 2020
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MATHEMATICA
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ldQ[n_]:=Module[{ldn=Max[IntegerDigits[n]], ldn1=Max[IntegerDigits[ n+1]]}, PrimeQ[ldn+ldn1]]; Select[Range[150], ldQ] (* Harvey P. Dale, Apr 29 2011 *)
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PROG
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(PARI) isok(m) = isprime(vecmax(digits(m))+vecmax(digits(m+1))); \\ Michel Marcus, May 20 2020
(Python)
def ok(n): return int(max(str(n))) + int(max(str(n+1))) in {2, 3, 5, 7, 11, 13, 17}
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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STATUS
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approved
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