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A293852 Numbers k such that (37*10^k + 377)/9 is prime. 0
1, 3, 9, 25, 36, 54, 108, 115, 147, 213, 465, 685, 768, 804, 1951, 3355, 12525, 15097, 15795, 22159, 95895, 185811 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 1 followed by the digits 53 is prime (see Example section).

a(23) > 2*10^5.

LINKS

Table of n, a(n) for n=1..22.

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

Makoto Kamada, Search for 41w53

EXAMPLE

3 is in this sequence because (37*10^3 + 377)/9 = 4153 is prime.

Initial terms and primes associated:

a(1) = 1, 83;

a(2) = 3, 4153;

a(3) = 9, 4111111153;

a(4) = 25, 41111111111111111111111153;

a(5) = 36, 4111111111111111111111111111111111153; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(37*10^# + 377)/9] &]

CROSSREFS

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

Sequence in context: A351937 A204448 A032681 * A005209 A112522 A005262

Adjacent sequences:  A293849 A293850 A293851 * A293853 A293854 A293855

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Oct 17 2017

EXTENSIONS

a(22) from Robert Price, Nov 02 2018

STATUS

approved

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Last modified June 28 21:04 EDT 2022. Contains 354907 sequences. (Running on oeis4.)