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A271640 Numbers k such that 3*10^k + 73 is prime. 0
1, 2, 5, 6, 13, 37, 50, 55, 71, 89, 217, 352, 355, 398, 449, 668, 742, 870, 1360, 1579, 2848, 3774, 5039, 5051, 6134, 6824, 7255, 12586, 17106, 27502, 30581, 33817, 97399, 170800, 172219, 177872 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k > 1, numbers such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 73 is prime (see Example section).

a(37) > 2*10^5.

LINKS

Table of n, a(n) for n=1..36.

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

Makoto Kamada, Search for 30w73.

EXAMPLE

5 is in this sequence because 3*10^5 + 73 = 300073 is prime.

Initial terms and primes associated:

a(1) = 1, 103;

a(2) = 2, 373;

a(3) = 5, 300073;

a(4) = 6, 3000073;

a(5) = 13, 30000000000073, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[3*10^# + 73] &]

PROG

(PARI) is(n)=ispseudoprime(3*10^n + 73) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A243799 A029544 A058668 * A180744 A092790 A105043

Adjacent sequences:  A271637 A271638 A271639 * A271641 A271642 A271643

KEYWORD

nonn,more

AUTHOR

Robert Price, Apr 11 2016

EXTENSIONS

a(34)-a(36) from Robert Price, Aug 10 2018

STATUS

approved

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Last modified April 22 04:04 EDT 2019. Contains 322329 sequences. (Running on oeis4.)