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 A173718 Numbers n such that (9^n - 2^n)/7 is prime. 2
 2, 3, 5, 13, 29, 37, 1021, 1399, 2137, 4493, 5521 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are prime. a(12) > 10^5. LINKS MATHEMATICA Select[ Prime[ Range[1, 100000] ], PrimeQ[ (9^# - 2^#)/7 ]& ] PROG (PARI) is(n)=ispseudoprime((9^n-2^n)/7) \\ Charles R Greathouse IV, Jun 06 2017 CROSSREFS Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032. Sequence in context: A289758 A089477 A099962 * A281316 A177502 A072536 Adjacent sequences:  A173715 A173716 A173717 * A173719 A173720 A173721 KEYWORD hard,more,nonn AUTHOR Robert Price, Dec 22 2012 STATUS approved

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