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 A103066 Numbers n such that 7*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 0, 1, 3, 6, 60, 288, 1314, 1728, 2493, 13893, 13944, 17100, 70227 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Also numbers n such that (71*10^n-53)/9 is prime. a(14) > 10^5. - Robert Price, Oct 06 2015 LINKS Makoto Kamada, Prime numbers of the form 788...883. FORMULA a(n) = A101151(n-1) + 1 for n>1. EXAMPLE For n=0, (71*10^n-53)/9 = 2 which is prime. MATHEMATICA Do[ If[ PrimeQ[(71*10^n - 53)/9], Print[n]], {n, 0, 10000}] PROG (PARI) for(n=0, 10^5, if(isprime((71*10^n-53)/9), print1(n", "))); \\ Altug Alkan, Oct 06 2015 CROSSREFS Cf. A002275, A101151. Sequence in context: A012473 A058161 A012877 * A145887 A219809 A137123 Adjacent sequences:  A103063 A103064 A103065 * A103067 A103068 A103069 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(10)-a(12) from Kamada data by Robert Price, Dec 14 2010 Inserted a(1)=0 and added a(13) by Robert Price, Oct 06 2015 STATUS approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)