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A276311 Numbers n such that (13*10^n + 197)/3 is prime. 0
1, 2, 4, 5, 17, 21, 23, 28, 41, 43, 51, 59, 105, 115, 131, 273, 585, 1519, 2303, 4791, 4921, 6019, 7833, 25711, 27319, 32497, 37975, 49381, 87199 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n>1, numbers such that the digit 4 followed by n-2 occurrences of the digit 3 followed by the digits 99 is prime (see the Example section).

a(30) > 10^5.

LINKS

Table of n, a(n) for n=1..29.

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

Makoto Kamada, Search for 43w99.

EXAMPLE

4 is in this sequence because (13*10^4 + 197)/3 = 43399 is prime.

Initial terms and primes associated:

a(1) = 1, 109;

a(2) = 2, 499;

a(3) = 4, 43399;

a(4) = 5, 433399;

a(5) = 17, 433333333333333399, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(13*10^# + 197)/3] &]

PROG

(PARI) is(n)=ispseudoprime((13*10^n+197)/3) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A169602 A092051 A065063 * A056440 A101843 A192117

Adjacent sequences:  A276308 A276309 A276310 * A276312 A276313 A276314

KEYWORD

nonn,more

AUTHOR

Robert Price, Aug 29 2016

STATUS

approved

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Last modified February 25 19:39 EST 2021. Contains 341618 sequences. (Running on oeis4.)