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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

Table of n, a(n) for n=1..6.

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 April 18 14:54 EDT 2019. Contains 322209 sequences. (Running on oeis4.)