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A293002 Numbers k such that (62*10^k - 791)/9 is prime. 0
2, 7, 10, 34, 53, 59, 62, 241, 298, 485, 731, 899, 1231, 4702, 7010, 8573, 9205, 9724, 17045, 24950 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For k>1, numbers such that the digit 6 followed by k-2 occurrences of the digit 8 followed by the digits 01 is prime (see Example section).

a(21) > 10^5.

LINKS

Table of n, a(n) for n=1..20.

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

Makoto Kamada, Search for 68w01

EXAMPLE

2 is in this sequence because (62*10^2 - 791)/9 = 601 is prime.

Initial terms and primes associated:

a(1) = 2, 601;

a(2) = 7, 68888801;

a(3) = 10, 68888888801;

a(4) = 34, 68888888888888888888888888888888801;

a(5) = 53, 688888888888888888888888888888888888888888888888888801; etc.

MATHEMATICA

Select[Range[1, 100000], PrimeQ[(62*10^# - 791)/9] &]

CROSSREFS

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

Sequence in context: A215407 A084184 A015963 * A056656 A151346 A247166

Adjacent sequences:  A292999 A293000 A293001 * A293003 A293004 A293005

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Sep 27 2017

STATUS

approved

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Last modified April 23 06:08 EDT 2019. Contains 322381 sequences. (Running on oeis4.)