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 A087512 Primes consisting only of digits 1 and 4 occurring with equal frequency. 5
 41, 14441411, 41414411, 44114141, 1144141441, 1144144411, 1144441141, 1411414441, 1441411441, 1441444111, 1444114141, 4111144441, 4111444411, 4114414141, 4141141441, 4141144141, 4144111441, 4411114441, 4411144141, 4411414411, 4414141141, 4414441111 (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 Union[Flatten[Table[Select[FromDigits/@Permutations[Flatten[Table[{1, 4}, {n}]]], PrimeQ], {n, 5}]]] (* Harvey P. Dale, Nov 21 2014 *) CROSSREFS Cf. A087510, A087513, A087514. Sequence in context: A297056 A292070 A297230 * A297055 A228555 A297058 Adjacent sequences: A087509 A087510 A087511 * A087513 A087514 A087515 KEYWORD base,nonn AUTHOR Paul D. Hanna and Amarnath Murthy, Sep 11 2003 EXTENSIONS More terms from Harvey P. Dale, Nov 21 2014 STATUS approved

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Last modified May 18 00:34 EDT 2024. Contains 372608 sequences. (Running on oeis4.)