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A066811
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Numbers k such that the concatenation of odd numbers from 1 to k is a prime.
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3
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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19 is a term because 135791113151719 is a prime.
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MATHEMATICA
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p = ""; Do[p = p <> ToString[2*n+1]; If[PrimeQ[ToExpression[p]], Print[2*n+1]], {n, 0, 2569}] (* Ryan Propper, Aug 26 2005 *)
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PROG
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(Python)
from sympy import isprime
def agen():
k, str1tok = 1, '1'
while True:
if isprime(int(str1tok)): yield k
k, str1tok = k + 2, str1tok + str(k + 2)
g = agen()
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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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EXTENSIONS
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STATUS
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approved
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