This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A102994 #17 Jan 17 2019 13:44:07
%S A102994 1,2,7,9,14,24,45,49,73,74,232,338,397,504,1063,2817,5305,16768,27060
%N A102994 Numbers n such that 4*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
%C A102994 Also numbers n such that (14*10^n-17)/3 is prime.
%C A102994 a(20) > 10^5. - _Robert Price_, May 27 2015
%H A102994 Makoto Kamada, <a href="https://stdkmd.net/nrr/4/46661.htm#prime">Prime numbers of the form 466...661</a>.
%H A102994 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F A102994 a(n) = A101729(n) + 1.
%t A102994 Do[ If[ PrimeQ[(14*10^n - 17)/3], Print[n]], {n, 0, 10000}]
%Y A102994 Cf. A002275, A101729.
%K A102994 more,nonn
%O A102994 1,2
%A A102994 _Robert G. Wilson v_, Jan 17 2005
%E A102994 Addition of a(18)-a(19) from Kamada data by _Robert Price_, Dec 10 2010