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Search: id:A108240
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| A108240 |
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Numbers n such that (10^n)^2 + 5*(10^n) - 1 is prime. |
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+0
1
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| 0, 1, 2, 7, 45, 54, 60, 99, 195, 271, 476, 1491, 2713
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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All of these primes 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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CROSSREFS
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Cf. A108195.
Sequence in context: A107354 A006118 A083670 this_sequence A064606 A066612 A098637
Adjacent sequences: A108237 A108238 A108239 this_sequence A108241 A108242 A108243
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KEYWORD
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more,nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Jun 17 2005
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