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 A110920 #20 Jan 17 2019 13:44:08 %S A110920 0,1,2,3,6,7,8,15,36,38,51,168,1000,2955,8151,16456,17902,18784,24948, %T A110920 28731,87144 %N A110920 Integers n such that 2*10^n + 81 is a prime number. %C A110920 See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "20081". %C A110920 a(22) > 10^5. - _Robert Price_, Jan 19 2017 %H A110920 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/">List of near-repdigit-related prime numbers</a>. %H A110920 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %e A110920 n = 3 is a term because 2*10^3 + 81 = 2*1000 + 81 = 2000 + 81 = 2081 and 2081 is prime. %Y A110920 Cf. A049054, A088274, A088275, A095688, A107083, A108049, A108050, A108052, A108054. %K A110920 more,nonn %O A110920 1,3 %A A110920 Julien Peter Benney (jpbenney(AT)ftml.net), Oct 04 2005 %E A110920 a(15)-a(18) from Kamada link by _Ray Chandler_, Dec 23 2010 %E A110920 a(1)-a(2) prepended by _Robert Price_, Jan 19 2017 %E A110920 a(19)-a(21) from _Robert Price_, Jan 19 2017