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A068692
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Largest n-digit prime with all even digits except for the least significant digit.
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3
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7, 89, 887, 8887, 88883, 888887, 8888861, 88888883, 888888887, 8888888809, 88888888801, 888888888887, 8888888888849, 88888888888889, 888888888888883, 8888888888888647, 88888888888888889, 888888888888888809
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OFFSET
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1,1
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LINKS
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MAPLE
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for n from 1 to 40 do a := prevprime((10^n-1)/9*8+2):b := convert(a, base, 10):c := true:for i from 2 to nops(b) do if((b[i] mod 2)>0) then c := false:end if:end do:while(c=false) do a := prevprime(a):b := convert(a, base, 10):c := true:for i from 2 to nops(b) do if((b[i] mod 2)>0) then c := false:end if:end do:end do:q[n] := a:end do:seq(q[k], k=1..40);
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MATHEMATICA
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nped[n_]:=Module[{p=NextPrime[9*10^n, -1]}, While[AnyTrue[Most[ IntegerDigits[ p]], OddQ], p=NextPrime[p, -1]]; p]; Array[nped, 20, 0] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 14 2018 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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