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A278418 Numbers k such that (83*10^k - 29) / 9 is prime. 0
1, 2, 4, 10, 28, 31, 32, 38, 68, 134, 158, 254, 311, 337, 392, 874, 2747, 3502, 4735, 6142, 14140, 17095, 20066, 21104, 26743 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k > 1, numbers such that the digit 9 followed by k-2 occurrences of the digit 2 followed by the digits 19 is prime (see Example section).

a(26) > 2*10^5.

LINKS

Table of n, a(n) for n=1..25.

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

Makoto Kamada, Search for 92w19.

EXAMPLE

4 is in this sequence because (83*10^4 - 29) / 9 = 92219 is prime.

Initial terms and primes associated:

a(1) = 1, 89;

a(2) = 2, 919;

a(3) = 4, 92219;

a(4) = 10, 92222222219;

a(5) = 28, 92222222222222222222222222219; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(83*10^# - 29) / 9] &]

PROG

(PARI) isok(n) = isprime((83*10^n - 29)/9); \\ Michel Marcus, Nov 21 2016

CROSSREFS

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

Sequence in context: A005975 A048193 A123411 * A321946 A244485 A128933

Adjacent sequences:  A278415 A278416 A278417 * A278419 A278420 A278421

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Nov 21 2016

STATUS

approved

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Last modified May 16 20:03 EDT 2022. Contains 353720 sequences. (Running on oeis4.)