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 A247260 Numbers n such that 5*6^n + 1 is prime. 5
 1, 2, 4, 17, 136, 147, 203, 590, 754, 964, 970, 1847, 2031, 2727, 2871, 5442, 7035, 7266, 11230, 23307, 27795, 34152, 42614, 127206, 133086 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(26) > 2*10^5. LINKS MATHEMATICA Do[ If[ PrimeQ[5*6^n + 1], Print[n]], {n, 0, 200000}] PROG (PARI) for(n=0, 2*10^5, if(ispseudoprime(5*6^n+1), print1(n, ", "))) \\ Derek Orr, Sep 10 2014 CROSSREFS Cf. A079906. Sequence in context: A009319 A009323 A307125 * A048872 A063800 A207137 Adjacent sequences:  A247257 A247258 A247259 * A247261 A247262 A247263 KEYWORD nonn,hard,more AUTHOR Robert Price, Sep 10 2014 STATUS approved

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Last modified January 18 19:50 EST 2020. Contains 331030 sequences. (Running on oeis4.)