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 A087513 Primes consisting only of digits 1 and 6 occurring with equal frequency. 7
 61, 16166611, 16616161, 61116661, 61661161, 66161611, 1166116661, 1166166161, 1166166611, 1166616161, 1616616611, 1661116661, 6111166661, 6111666611, 6116116661, 6161161661, 6161166161, 6161166611, 6161661161, 6166111661 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 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 Harvey P. Dale, Table of n, a(n) for n = 0..5000 MAPLE Primes consisting only of digits x and y, occurring with equal frequency. 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) MATHEMATICA Table[Select[FromDigits/@Permutations[PadRight[{}, 2*n, {1, 6}]], PrimeQ], {n, 5}]//Flatten//Sort (* Harvey P. Dale, May 28 2019 *) CROSSREFS Cf. A087510, A087514, A087515. Sequence in context: A116124 A068533 A093631 * A176272 A173418 A147667 Adjacent sequences: A087510 A087511 A087512 * A087514 A087515 A087516 KEYWORD base,nonn AUTHOR Amarnath Murthy and Paul D. Hanna, Sep 11 2003 STATUS approved

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Last modified May 19 00:35 EDT 2024. Contains 372666 sequences. (Running on oeis4.)