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A093162 Primes of the form 20*R_n + 3, where R_n is the repunit (A002275) of length n. 3

%I

%S 3,23,223,22222223,22222222223,222222222222222222222222222222222223

%N Primes of the form 20*R_n + 3, where R_n is the repunit (A002275) of length n.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/2/22223.htm#prime">Prime numbers of the form 22...223</a>.

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

%F a(n) = (20*10^A056656(n) + 7)/9 = (2*10^A096506(n) + 7)/9.

%Y Cf. A002275, A056656 (corresponding n, and count of digits 2 in a(n)), A096506.

%K nonn

%O 1,1

%A _Rick L. Shepherd_, Mar 26 2004

%E Edited by _Ray Chandler_, Feb 27 2012

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)