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A282278 Numbers k such that (22*10^k + 161)/3 is prime. 0
0, 1, 2, 4, 5, 6, 7, 13, 28, 36, 40, 74, 233, 425, 828, 888, 1970, 2119, 2338, 2971, 3030, 14005, 20190, 29589, 47034, 47292, 51457, 64326, 70259, 90110 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For k>1, numbers such that the digit 7 followed by k-2 occurrences of the digit 3 followed by the digits 87 is prime (see Example section).

a(31) > 10^5.

LINKS

Table of n, a(n) for n=1..30.

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

Makoto Kamada, Search for 73w87.

EXAMPLE

4 is in this sequence because (22*10^4 + 161)/3 = 73387 is prime.

Initial terms and primes associated:

a(1) = 0, 61;

a(2) = 1, 127;

a(3) = 2, 787;

a(4) = 4, 73387;

a(5) = 5, 733387; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(22*10^# + 161)/3] &]

CROSSREFS

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

Sequence in context: A276005 A092058 A134532 * A268448 A230581 A248962

Adjacent sequences:  A282275 A282276 A282277 * A282279 A282280 A282281

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 10 2017

STATUS

approved

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Last modified February 22 02:01 EST 2019. Contains 320381 sequences. (Running on oeis4.)