A103052 - OEIS

A103052

Numbers n such that 7*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 4, 16, 25, 29, 41, 47, 88, 1132, 1570, 3985, 10609, 12175, 29369

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OFFSET

1,2

COMMENTS

Also numbers n such that (65*10^n-11)/9 is prime.

a(15) > 10^5. - Robert Price, Sep 23 2015

LINKS

FORMULA

a(n) = A101133(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(65*10^n - 11)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

KEYWORD

more,nonn

AUTHOR

EXTENSIONS

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

STATUS

approved