A103084 - OEIS

A103084

Numbers n such that 8*10^n + 5*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 7, 44, 56, 338, 1211, 2693, 3536, 3917, 3974, 4046, 6961, 23771, 69656

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OFFSET

1,2

COMMENTS

Also numbers n such that (77*10^n-23)/9 is prime.

a(16) > 10^5. - Robert Price, Oct 22 2015

LINKS

FORMULA

a(n) = A101071(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(77*10^n - 23)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) for(n=0, 1e5, if(isprime((77*10^n-23)/9), print1(n, ", "))) \\ Altug Alkan, Oct 22 2015

CROSSREFS

KEYWORD

more,nonn

AUTHOR

EXTENSIONS

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

a(15) from Robert Price, Oct 22 2015

STATUS

approved