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A093139 Primes of the form 10*R_n + 7, where R_n is the repunit (A002275) of length n. 1

%I

%S 7,17,1117,11117,11111117,11111111111111111111117,

%T 11111111111111111111111111117,

%U 1111111111111111111111111111111111111117

%N Primes of the form 10*R_n + 7, where R_n is the repunit (A002275) of length n.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/11117.htm#prime">Prime numbers of the form 11...117</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>

%Y Cf. A056655 (corresponding n).

%K nonn

%O 1,1

%A _Rick L. Shepherd_, Mar 23 2004

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Last modified June 1 09:53 EDT 2020. Contains 334762 sequences. (Running on oeis4.)