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A272621 Numbers n such that 10^n-9^(n-1) is prime. 0
3, 9, 15, 155, 217, 281, 287, 491, 563, 581, 983, 2243, 4375, 8409, 98669 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(16) > 10^5.

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

3 is a member since 10^3-9^2 = 1000-81 = 919 which is a prime number.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[10^# - 9^(# - 1)] &]

PROG

(PARI) is(n)=ispseudoprime(10^n-9^(n-1)) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A093713, A082103, A093717, A093793, A096185, A093765, A093794, A093795, A096186.

Sequence in context: A242438 A083556 A015664 * A134137 A174179 A076362

Adjacent sequences:  A272618 A272619 A272620 * A272622 A272623 A272624

KEYWORD

nonn,more

AUTHOR

Robert Price, May 03 2016

STATUS

approved

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Last modified October 24 08:15 EDT 2021. Contains 348217 sequences. (Running on oeis4.)