A103076 Numbers n such that 8*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 2, 20, 33, 62, 68, 86, 195, 524, 530, 657, 1874, 2198, 62072, 73076

Offset

1,2

Comments

Also numbers n such that (74*10^n+43)/9 is prime.

a(16) > 10^5. - Robert Price, Oct 19 2015

Links

Table of n, a(n) for n=1..15.

Makoto Kamada, Prime numbers of the form 822...227.

Index entries for primes involving repunits.

Formula

a(n) = A101063(n-1) + 1, for n>1.

Mathematica

Do[ If[ PrimeQ[(74*10^n + 43)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) for(n=0, 1e3, if(isprime((74*10^n+43)/9), print1(n", "))) \\ Altug Alkan, Oct 19 2015

Crossrefs

Cf. A002275, A101063.

Sequence in context: A061471 A112271 A201122 * A293029 A298761 A062133

Adjacent sequences: A103073 A103074 A103075 * A103077 A103078 A103079

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

Inserted a(1)=0 and added a(14)-a(15) by Robert Price, Oct 19 2015

Status

approved