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 A102976 Numbers k such that 3*10^k + 7*R_k - 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k. 1
 1, 5, 71, 112, 115, 173, 263, 310, 358, 10499, 22925, 37957, 254195, 463649 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers k such that (34*10^k-61)/9 is prime. a(15) > 8*10^5. - Jason H Parker, Sep 30 2021 LINKS Makoto Kamada, Prime numbers of the form 377...771. FORMULA a(n) = A101841(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(34*10^k-61)/9], Print[k]], {k, 1, 10000}] CROSSREFS Cf. A002275, A101841. Sequence in context: A248367 A157860 A125242 * A141852 A142052 A139930 Adjacent sequences:  A102973 A102974 A102975 * A102977 A102978 A102979 KEYWORD nonn,more AUTHOR Robert G. Wilson v, Dec 17 2004 EXTENSIONS Addition of a(10)-a(11) from Kamada data by Robert Price, Dec 13 2010 a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 a(13) from Jason H Parker, Jun 14 2019 0 removed by Georg Fischer, Jan 03 2021 a(14) from Jason H Parker, Sep 30 2021 STATUS approved

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Last modified December 3 12:47 EST 2021. Contains 349463 sequences. (Running on oeis4.)