A282975 - OEIS

A282975

Numbers k such that (134*10^k + 7)/3 is prime.

0, 1, 6, 13, 18, 28, 40, 45, 50, 70, 101, 210, 248, 298, 1246, 1340, 1586, 2466, 6548, 6713, 7394, 23904, 32450, 38171, 39120, 67816, 108610, 112400, 129038

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OFFSET

1,3

COMMENTS

For k > 0, numbers k such that the digits 44 followed by k-1 occurrences of the digit 6 followed by the digit 9 is prime (see Example section).

a(30) > 2*10^5.

LINKS

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

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

Makoto Kamada, Search for 446w9.

EXAMPLE

1 is in this sequence because (134*10^1 + 7)/3 = 449 is prime.

Initial terms and associated primes:

a(1) = 0, 47;

a(2) = 1, 449;

a(3) = 6, 44666669;

a(4) = 13, 446666666666669;

a(5) = 18, 44666666666666666669; etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(134*10^# + 7)/3] &]

PROG

(PARI) isok(k) = isprime((134*10^k + 7)/3); \\ Michel Marcus, Feb 26 2017

CROSSREFS

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

Sequence in context: A153696 A032366 A287237 * A094696 A095911 A013575

Adjacent sequences: A282972 A282973 A282974 * A282976 A282977 A282978

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Feb 26 2017

EXTENSIONS

a(27)-a(29) from Robert Price, Feb 05 2020

STATUS

approved