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A179033 Emirps with a single 2 as the only prime digit. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
Note that 2 and 929 are not emirps because they are palindromes.
MAPLE
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:
sort([Res]); # Robert Israel, Jun 02 2016
MATHEMATICA
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 *)
CROSSREFS
Sequence in context: A088290 A209620 A179032 * A082059 A081633 A020388
KEYWORD
base,less,nonn
AUTHOR
Lekraj Beedassy, Jun 25 2010
EXTENSIONS
Terms confirmed by Ray Chandler, Jul 13 2010
Definition improved by Harvey P. Dale, Jul 17 2010
STATUS
approved

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Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)