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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
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
Sequence in context: A297056 A292070 A297230 * A297055 A228555 A297058
KEYWORD
base,nonn
AUTHOR
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.)