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 A108312 #24 Jan 17 2019 13:44:08
%S A108312 1,2,83,167,242,14081,65537
%N A108312 Integers n such that 10^n + 27 is prime.
%C A108312 The next term, if one exists, is >100000. - _Robert Price_, May 24 2010
%C A108312 See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "10027".
%H A108312 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/">List of near-repdigit-related prime numbers</a>.
%H A108312 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%e A108312 For n=2 we have 10^2 + 27 = 100 + 27 = 127, which is prime.
%t A108312 Do[ If[ PrimeQ[10^n + 27], Print[n]], {n, 3000}] (* _Robert G. Wilson v_, Jul 01 2005 *)
%Y A108312 Cf. A049054, A088274, A088275, A095688, A107083, A108049, A108050, A108052, A108054.
%K A108312 more,nonn
%O A108312 1,2
%A A108312 Julien Peter Benney (jpbenney(AT)ftml.net), Jun 29 2005
%E A108312 a(6)=14081 from _Robert Price_, Mar 22 2010
%E A108312 Edited by _Ray Chandler_, Dec 23 2010
%E A108312 a(7)=65537 from _Robert Price_, Jan 29 2011