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A234965
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Numbers n such that 123...n - (n+1) is prime.
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0
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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1234 - 5 = 1229 is prime so 4 is a member of this sequence.
123456 - 7 = 123449 is prime so 6 is a member of this sequence.
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MATHEMATICA
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c = 0; Do[c = n + c*10^IntegerLength[n]; If[PrimeQ[c-n-1)], Print@n], {n, 1700}] (* Giovanni Resta, Jan 11 2014 *)
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PROG
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(Python)
def Concatenate(x):
..num = ''
..for n in range(1, x+1):
....num += str(n)
..return int(num)
import sympy
from sympy import isprime
{print(x) for x in range(1, 10**3) if isprime(Concatenate(x)-(x+1))}
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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