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A294918 Numbers k such that 4*10^k + 39 is prime. 0
0, 1, 2, 4, 6, 12, 19, 23, 24, 86, 110, 120, 258, 359, 584, 1144, 2833, 10346, 13333, 23238, 29546, 44356, 59292 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For k > 1, numbers such that the digit 4 followed by k-2 occurrences of the digit 0 followed by the digits 39 is prime (see Example section).

a(24) > 2*10^5.

LINKS

Table of n, a(n) for n=1..23.

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

Makoto Kamada, Search for 40w39

EXAMPLE

2 is in this sequence because 4*10^2 + 39 = 439 is prime.

Initial terms and primes associated:

a(1) = 0, 43;

a(2) = 1, 79;

a(3) = 2, 439;

a(4) = 4, 40039;

a(5) = 6, 4000039; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[4*10^# + 39] &]

CROSSREFS

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

Sequence in context: A243543 A094769 A068018 * A331872 A307067 A060798

Adjacent sequences:  A294915 A294916 A294917 * A294919 A294920 A294921

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Nov 10 2017

STATUS

approved

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Last modified April 13 12:29 EDT 2021. Contains 342936 sequences. (Running on oeis4.)