A103036 - OEIS

%I #19 Jan 17 2019 13:44:07

%S 1,2,5,10,40,47,58,73,92,113,124,130,887,1234,1538,2063,2591,2786,

%T 3145,21688,32381,39170,47791,83878

%N Numbers n such that 6*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

%C Also numbers n such that (58*10^n+23)/9 is prime.

%C a(25) > 10^5. - _Robert Price_, Sep 15 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/6/64447.htm#prime">Prime numbers of the form 644...447</a>.

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

%F a(n) = A101529(n) + 1.

%t Do[ If[ PrimeQ[(58*10^n + 23)/9], Print[n]], {n, 0, 10000}]

%Y Cf. A002275, A101529.

%K more,nonn

%O 1,2

%A _Robert G. Wilson v_, Jan 18 2005

%E a(20) from Kamada data by _Robert Price_, Dec 14 2010

%E a(21)-a(23) from Erik Branger May 01 2013 by _Ray Chandler_, Aug 16 2013

%E a(24) from _Robert Price_, Sep 15 2015