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Search: id:A087527
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| A087527 |
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Primes consisting only of digits 2 and 3 occurring with equal frequency. |
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+0
1
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| 23, 23223323, 32323223, 2222323333, 2223223333, 2232223333, 2232322333, 2232332233, 2323222333, 2332322233, 2333222323, 2333223223, 3223232323, 3232222333, 3232232233, 3232233223, 3232322323, 3323232223, 23322322233323
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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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).
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MAPLE
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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)
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CROSSREFS
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Cf. A087510, A087511, A087514.
Sequence in context: A050234 A124993 A013818 this_sequence A013906 A030464 A053558
Adjacent sequences: A087524 A087525 A087526 this_sequence A087528 A087529 A087530
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KEYWORD
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base,nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com) and Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 12 2003
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