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A179033 Emirps with a single 2 as the only prime digit. 2


%S 1021,1201,1249,1429,9029,9209,9241,9421,10429,11621,12109,12119,

%T 12149,12491,12611,12619,12641,12689,12809,12841,12919,14029,14621,

%U 14629,14821,14929,16249,16829,18269,19219,19249,19421,90121,90821,91121

%N Emirps with a single 2 as the only prime digit.

%H Robert Israel, <a href="/A179033/b179033.txt">Table of n, a(n) for n = 1..10000</a>

%e Note that 2 and 929 are not emirps because they are palindromes.

%p Dmax:= 6: # to get all terms with up to Dmax digits

%p Res:= NULL:

%p npd:= [0,1,4,6,8,9]:

%p for dd from 3 to Dmax do

%p R:= [seq(seq([seq(npd[j+1],j=convert(6*x+j,base,6))],

%p x=[$6^(dd-3) .. 2*6^(dd-3)-1, $5*6^(dd-3)..6^(dd-2)-1]),j=[1,5])];

%p for p from 2 to dd-1 do

%p for r in R do

%p x:= [op(r[1..p-1]),2,op(r[p..-1])];

%p v1:= add(x[i]*10^(i-1),i=1..dd);

%p v2:= add(x[-i]*10^(i-1),i=1..dd);

%p 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

%p od od od:

%p sort([Res]); # _Robert Israel_, Jun 02 2016

%t emrp[n_]:=Module[{idn=IntegerDigits[n],rev},rev=Reverse[idn];PrimeQ[FromDigits[rev]]&&rev!=idn]

%t only2[n_]:=DigitCount[n,10,{3,5,7}]=={0,0,0}&&DigitCount[n,10,2]==1

%t Select[Select[Prime[Range[10000]],emrp],only2] (* _Harvey P. Dale_, Jan 22 2011 *)

%Y Cf. A006567, A179032.

%K base,less,nonn

%O 1,1

%A _Lekraj Beedassy_, Jun 25 2010

%E Terms confirmed by _Ray Chandler_, Jul 13 2010

%E Definition improved by _Harvey P. Dale_, Jul 17 2010

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Last modified March 22 22:02 EDT 2023. Contains 361434 sequences. (Running on oeis4.)