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A179033
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Emirps with a single 2 as the only prime digit.
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2
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1021, 1201, 1249, 1429, 9029, 9209, 9241, 9421, 10429, 11621, 12109, 12119, 12149, 12491, 12611, 12619, 12641, 12689, 12809, 12841, 12919, 14029, 14621, 14629, 14821, 14929, 16249, 16829, 18269, 19219, 19249, 19421, 90121, 90821, 91121
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OFFSET
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1,1
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LINKS
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EXAMPLE
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Note that 2 and 929 are not emirps because they are palindromes.
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MAPLE
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Dmax:= 6: # to get all terms with up to Dmax digits
Res:= NULL:
npd:= [0, 1, 4, 6, 8, 9]:
for dd from 3 to Dmax do
R:= [seq(seq([seq(npd[j+1], j=convert(6*x+j, base, 6))],
x=[$6^(dd-3) .. 2*6^(dd-3)-1, $5*6^(dd-3)..6^(dd-2)-1]), j=[1, 5])];
for p from 2 to dd-1 do
for r in R do
x:= [op(r[1..p-1]), 2, op(r[p..-1])];
v1:= add(x[i]*10^(i-1), i=1..dd);
v2:= add(x[-i]*10^(i-1), i=1..dd);
if v1 < v2 and isprime(v1) and isprime(v2) then Res:= Res, v1, v2; if min(v1, v2) < 10^3 then print(dd, p, r, x, v1, v2) fi fi
od od od:
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MATHEMATICA
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emrp[n_]:=Module[{idn=IntegerDigits[n], rev}, rev=Reverse[idn]; PrimeQ[FromDigits[rev]]&&rev!=idn]
only2[n_]:=DigitCount[n, 10, {3, 5, 7}]=={0, 0, 0}&&DigitCount[n, 10, 2]==1
Select[Select[Prime[Range[10000]], emrp], only2] (* Harvey P. Dale, Jan 22 2011 *)
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CROSSREFS
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KEYWORD
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base,less,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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