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A273868 Numbers n such that 10^n-9^(n+1) is prime. 0
25, 51, 91, 107, 145, 651, 1473, 2145, 5577, 12457 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(11) > 10^5.

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

25 is a member since 10^25 - 9^26 = 3538918110773326701067759 which is a prime number.

MATHEMATICA

Select[Range[21, 100000], PrimeQ[10^# - 9^(# + 1)] &]

PROG

(PARI) is(n)=ispseudoprime(10^n-9^(n+1)) \\ Charles R Greathouse IV, Jun 08 2016

CROSSREFS

Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883.

Sequence in context: A042238 A042234 A042232 * A270693 A042240 A042242

Adjacent sequences:  A273865 A273866 A273867 * A273869 A273870 A273871

KEYWORD

nonn,more

AUTHOR

Robert Price, Jun 01 2016

STATUS

approved

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Last modified October 18 01:01 EDT 2018. Contains 316297 sequences. (Running on oeis4.)