A103041 - OEIS

A103041

Numbers n such that 6*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 5, 8, 17, 20, 65, 83, 90, 108, 252, 335, 1488, 6356, 65712, 96798

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OFFSET

1,1

COMMENTS

Also numbers n such that (59*10^n+31)/9 is prime.

a(16) > 10^5. - Robert Price, Sep 13 2015

LINKS

FORMULA

a(n) = A101534(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(59*10^n + 31)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) is(n)=isprime(6*10^n + 5*(10^n-1)/9 + 4) \\ Anders Hellström, Sep 13 2015

CROSSREFS

KEYWORD

more,nonn

AUTHOR

EXTENSIONS

a(14)-a(15) from Robert Price, Sep 13 2015

STATUS

approved