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A269797 Numbers n such that (29*10^n+91)/3 is prime. 0
1, 2, 3, 4, 8, 11, 18, 27, 39, 54, 55, 65, 75, 83, 111, 164, 189, 191, 204, 252, 322, 371, 449, 646, 678, 754, 1641, 5210, 7787, 11691, 13682, 15994, 22356, 29203, 35756, 57834, 64027, 72985, 74276 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Except for the smallest terms, numbers n such that digit 9 followed by n-2 occurrences of digit 6 followed by the digits 97 is prime (see Example section).

a(40) > 10^5.

LINKS

Table of n, a(n) for n=1..39.

Makoto Kamada, Search for 96w97.

EXAMPLE

6 is in this sequence because (266*10^n+1)/3 = 88666667 is prime.

Initial terms and primes associated:

a(1) = 1, 127

a(2) = 2, 997

a(3) = 3, 9697

a(4) = 4, 96697

a(5) = 8, 966666697

a(6) = 11, 966666666697

a(7) = 18, 9666666666666666697

a(8) = 27, 9666666666666666666666666697

a(9) = 39, 9666666666666666666666666666666666666697 etc.

MATHEMATICA

Select[Range[0, 100000], PrimeQ[(29*10^#+91)/3] &]

PROG

(PARI) isok(n) = isprime((29*10^n+91)/3); \\ Michel Marcus, Mar 05 2016

CROSSREFS

Cf. A056654, A268448, A269303.

Sequence in context: A015935 A135909 A046812 * A280195 A286224 A245388

Adjacent sequences:  A269794 A269795 A269796 * A269798 A269799 A269800

KEYWORD

nonn,more

AUTHOR

Robert Price, Mar 05 2016

STATUS

approved

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Last modified April 21 10:30 EDT 2019. Contains 322328 sequences. (Running on oeis4.)