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 A217095 Numbers n such that (10^n + 9^n)/19 is prime. 12
 7, 67, 73, 1091, 1483, 10937 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The numbers n themselves (7, 67, 73, ...) are also prime. a(7) > 10^5. LINKS MATHEMATICA Select[ Prime[ Range[1, 100000] ], PrimeQ[ (10^# + 9^#)/19 ]& ] PROG (PARI) is(n)=isprime((10^n+9^n)/19) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A057175, A125956, A128339, A181141, A187819. Sequence in context: A197744 A052351 A210476 * A106111 A261184 A142786 Adjacent sequences:  A217092 A217093 A217094 * A217096 A217097 A217098 KEYWORD hard,nonn,more AUTHOR Robert Price, Feb 17 2013 STATUS approved

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Last modified October 23 09:45 EDT 2019. Contains 328345 sequences. (Running on oeis4.)