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A108240
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Numbers k such that (10^k)^2 + 5*(10^k) - 1 is prime.
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0
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0, 1, 2, 7, 45, 54, 60, 99, 195, 271, 476, 1491, 2713, 8155
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OFFSET
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1,3
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COMMENTS
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All of the primes for the terms <= 2713 have been certified. Primality proof for the largest: PFGW Version 20041001.Win_Stable (v1.2 RC1b) [FFT v23.8] Primality testing (10^2713)^2+5*(10^2713)-1 [N+1, Brillhart-Lehmer-Selfridge] Running N+1 test using discriminant 7, base 1+sqrt(7) Calling Brillhart-Lehmer-Selfridge with factored part 34.96% (10^2713)^2+5*(10^2713)-1 is prime! (216.4510s+10.6592s)
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LINKS
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PROG
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CROSSREFS
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KEYWORD
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more,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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