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A069749
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Number of primes less than 10^n containing only the digits 2 and 3 (A020458).
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0
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2, 3, 5, 7, 11, 18, 31, 44, 83, 135, 239, 436, 818, 1436, 2773, 4695, 9244, 17022, 32948, 58158, 116040, 214188
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OFFSET
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1,1
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COMMENTS
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a(22) / A006880(22) = 214188 / 201467286689315906290 =~ 10^-15. But out of the 2^22 candidates for primes, ~5% are.
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LINKS
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MATHEMATICA
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s = 0; Do[k = 0; While[k < 2^n, k++; If[p = FromDigits[ PadLeft[ IntegerDigits[k, 2], n] + 2]; PrimeQ[p], s++ ]]; Print[s], {n, 1, 22}]
With[{c=Select[Flatten[Table[FromDigits/@Tuples[{2, 3}, n], {n, 22}]], PrimeQ]}, Table[Count[c, _?(#<10^i&)], {i, 22}]] (* Harvey P. Dale, Mar 18 2016 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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