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A274336 Numbers k such that (16*10^k - 91)/3 is prime. 0
1, 2, 3, 5, 16, 18, 22, 31, 40, 98, 99, 192, 233, 367, 501, 1102, 1381, 1416, 2018, 6156, 6860, 7377, 14004, 16634, 21422, 27654, 85473 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For k>1, numbers n such that the digit 5 followed by k-1 occurrences of the digit 3 followed by the digits 03 is prime (see Example section).

a(28) > 2*10^5.

LINKS

Table of n, a(n) for n=1..27.

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

Makoto Kamada, Search for 53w03.

EXAMPLE

3 is in this sequence because (16*10^3 - 91)/3 = 5303 is prime.

Initial terms and primes associated:

a(1) = 1, 23;

a(2) = 2, 503;

a(3) = 3, 5303;

a(4) = 5, 533303;

a(5) = 16, 53333333333333303, etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(16*10^# - 91)/3] &]

PROG

(PARI) is(n)=ispseudoprime((16*10^n - 91)/3) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A330821 A248827 A273525 * A192648 A219339 A048112

Adjacent sequences:  A274333 A274334 A274335 * A274337 A274338 A274339

KEYWORD

nonn,more

AUTHOR

Robert Price, Jun 22 2016

STATUS

approved

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Last modified February 28 04:39 EST 2020. Contains 332321 sequences. (Running on oeis4.)