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A275323 Numbers n such that (19*10^n + 161)/9 is prime. 0
2, 3, 5, 6, 8, 18, 36, 59, 80, 162, 197, 200, 405, 432, 930, 1065, 1496, 1716, 3213, 5712, 6303, 7466, 14150, 23685, 54608, 59766 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For n>1, numbers n such that the digit 2 followed by n-2 occurrences of the digit 1 followed by the digits 29 is prime (see Example section).

a(27) > 10^5.

LINKS

Table of n, a(n) for n=1..26.

Makoto Kamada, Factorization of near-repdigit-related numbers.

Makoto Kamada, Search for 21w29.

EXAMPLE

5 is in this sequence because (19*10^5 + 161)/9 = 211129 is prime.

Initial terms and primes associated:

a(1) = 2, 229;

a(2) = 3, 2129;

a(3) = 5, 211129;

a(4) = 6, 2111129;

a(5) = 8, 211111129, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(19*10^# + 161)/9] &]

PROG

(PARI) is(n)=ispseudoprime((19*10^n+161)/9) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

Sequence in context: A088497 A088485 A194626 * A128994 A098211 A218013

Adjacent sequences:  A275320 A275321 A275322 * A275324 A275325 A275326

KEYWORD

nonn,more

AUTHOR

Robert Price, Jul 23 2016

STATUS

approved

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Last modified July 17 08:42 EDT 2019. Contains 325098 sequences. (Running on oeis4.)