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A103066 Numbers n such that 7*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 3, 6, 60, 288, 1314, 1728, 2493, 13893, 13944, 17100, 70227 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (71*10^n-53)/9 is prime.

a(14) > 10^5. - Robert Price, Oct 06 2015

LINKS

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 788...883.

Index entries for primes involving repunits.

FORMULA

a(n) = A101151(n-1) + 1 for n>1.

EXAMPLE

For n=0, (71*10^n-53)/9 = 2 which is prime.

MATHEMATICA

Do[ If[ PrimeQ[(71*10^n - 53)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) for(n=0, 10^5, if(isprime((71*10^n-53)/9), print1(n", "))); \\ Altug Alkan, Oct 06 2015

CROSSREFS

Cf. A002275, A101151.

Sequence in context: A012473 A058161 A012877 * A145887 A219809 A137123

Adjacent sequences:  A103063 A103064 A103065 * A103067 A103068 A103069

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(10)-a(12) from Kamada data by Robert Price, Dec 14 2010

Inserted a(1)=0 and added a(13) by Robert Price, Oct 06 2015

STATUS

approved

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)