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 A224691 Numbers n such that (13^n - 4^n)/9 is prime. 1
 2, 5, 19, 109, 157, 8521, 26017, 26177 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are prime. a(9) > 10^5. LINKS MATHEMATICA Select[Prime[Range[1, 100000]], PrimeQ[(13^# - 4^#)/9]&] PROG (PARI) is(n)=ispseudoprime((13^n-4^n)/9) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347. Sequence in context: A211207 A107882 A328977 * A192445 A089126 A113346 Adjacent sequences:  A224688 A224689 A224690 * A224692 A224693 A224694 KEYWORD nonn,hard,more AUTHOR Robert Price, Apr 15 2013 STATUS approved

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Last modified November 27 04:21 EST 2020. Contains 338677 sequences. (Running on oeis4.)