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 A106488 Numbers n such that 1_666.2_666.3_666 ... 8_666.9_666.10^n+1 is prime, i.e., 1 repeated 666 times, concatenated with 2 repeated 666 times, etc. 1
 641, 1788, 1918, 3731, 7093, 8009 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS These are "subscript" primes, similar to those listed in Table 30 of the Primal Configurations document. Only 3731, 7093 and 8009 have been proved prime. The others are Fermat and Lucas PRPs. Primality proof for the largest (14003 digits): PFGW Version 20041001.Win_Stable (v1.2 RC1b) [FFT v23.8] Primality testing (r(666,1)*10^5328+r(666,2)*10^4662+r(666,3)*10^3996+r(666,4)*10^3330+r(666,5)*10^2664+r(666,6)*10^1998+r(666,7)*10^1332+r(666,8)*10^666+r(666,9))*10^8009+1 [N-1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 17 (r(666,1)*10^5328+r(666,2)*10^4662+r(666,3)*10^3996+r(666,4)*10^3330+r(666,5)*10^2664+r(666,6)*10^1998+r(666,7)*10^1332+r(666,8)*10^666+r(666,9))*10^8009+1 is prime! (38.8002s+0.0106s) LINKS Table of n, a(n) for n=1..6. R. Ondrejka, The Top Ten: a Catalogue of Primal Configurations. CROSSREFS Sequence in context: A252434 A105130 A117129 * A259997 A256806 A206164 Adjacent sequences: A106485 A106486 A106487 * A106489 A106490 A106491 KEYWORD base,nonn AUTHOR Jason Earls, May 29 2005 STATUS approved

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Last modified February 25 17:53 EST 2024. Contains 370332 sequences. (Running on oeis4.)