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 A177866 #22 Jan 17 2019 13:44:08 %S A177866 2,4,6,7,8,14,20,110,138,140,145,300,390,1484,3194,3300,3950,4986, %T A177866 5574,5630,5874,8866,11390,45130,86110 %N A177866 Numbers n such that 10^n - 69 is prime. %C A177866 The next term, if it exists, is > 100000. %C A177866 See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "99931". %H A177866 <a href="/A177866/b177866.txt">Table of n, a(n) for n = 1..25</a> %H A177866 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/">List of near-repdigit-related prime numbers</a>. %H A177866 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %e A177866 10^6 - 69 = 999931 which is a prime number. %t A177866 m=1000; For[n=1, n<m, If[PrimeQ[10^n-69], Print[n]]; n++ ] %o A177866 (PARI) is(n)=ispseudoprime(10^n-69) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A177866 Cf. A108330, A108328. %K A177866 more,nonn %O A177866 1,1 %A A177866 _Robert Price_, Dec 28 2010 %E A177866 a(24-25)=45130,86110 from _Robert Price_, May 29 2011