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A295386 Numbers k such that (188*10^k + 7)/3 is prime. 0
2, 29, 35, 44, 51, 75, 101, 116, 131, 285, 320, 537, 581, 617, 1149, 1751, 2957, 3015, 31493, 166611 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For k > 1, numbers such that the digits 62 followed by k-1 occurrences of the digit 6 followed by the digit 9 is prime (see Example section).

a(21) > 2*10^5.

LINKS

Table of n, a(n) for n=1..20.

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

Makoto Kamada, Search for 626w9.

EXAMPLE

2 is in this sequence because (188*10^2 + 7)/3 = 6269 is prime.

Initial terms and primes associated:

a(1) = 2, 6269;

a(2) = 29, 6266666666666666666666666666669;

a(3) = 35, 6266666666666666666666666666666666669;

a(4) = 44, 6266666666666666666666666666666666666666666669; etc..

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(188*10^# + 7)/3] &]

CROSSREFS

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

Sequence in context: A019379 A107166 A041969 * A019392 A060503 A180231

Adjacent sequences:  A295383 A295384 A295385 * A295387 A295388 A295389

KEYWORD

nonn,more,hard

AUTHOR

Robert Price, Nov 21 2017

EXTENSIONS

a(20) from Robert Price, Mar 21 2020

STATUS

approved

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Last modified July 5 19:02 EDT 2020. Contains 335473 sequences. (Running on oeis4.)