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A087530 Primes consisting only of digits 3 and 5 occurring with equal frequency. 3
53, 35553533, 53355353, 53533553, 3335553553, 3355335553, 3355355533, 3355533553, 3355535353, 3535355353, 3553535353, 3553555333, 3555353353, 3555353533, 3555533533, 5353353553, 5353533553, 5353553533, 5355353533 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
There are 18 digit pairs which can produce such primes. (1,0),(7,0),(1,3),(1,4),(1,6),(1,7),(1,9),(2,3),(2,9),(3,4),(3,5),(3,7),(3,8),(4,7),(4,9),(5,9),(6,7),(7,9).
LINKS
MATHEMATICA
Sort[Select[FromDigits/@Flatten[Permutations/@Table[PadRight[{}, 2n, {3, 5}], {n, 5}], 1], PrimeQ]] (* Harvey P. Dale, Oct 24 2012 *)
PROG
(PARI) /* Primes consisting only of digits x and y, occurring with equal frequency. */ x=3; y=5; d1=x; d2=y; k=0; a=vector(100); for(n=1, 3000, B=binary(n); L=length(B); s=sum(j=1, length(B), B[j]); if(L%2==0 & s==L/2, C=vector(L, n, (d2-d1)*B[n]+d1); p=subst(Pol(C), x, 10); if(isprime(p), if(k<100, k++; a[k]=p)); D=vector(L, n, d2-(d2-d1)*B[n]); q=subst(Pol(D), x, 10); if(isprime(q ), if(k<100, k++; a[k]=q))); ); a=vector(k, n, a[n]); vecsort(a)
CROSSREFS
Sequence in context: A336440 A368298 A145332 * A125037 A101365 A022080
KEYWORD
base,nonn
AUTHOR
EXTENSIONS
Edited by Charles R Greathouse IV, Oct 28 2009
STATUS
approved

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Last modified July 13 09:13 EDT 2024. Contains 374274 sequences. (Running on oeis4.)