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 A178429 #26 Jan 17 2019 13:44:08 %S A178429 4,48,64,313,484,642,11950,15845,18580,50929 %N A178429 Numbers n such that 10^n - 51 is prime. %H A178429 Makoto Kamada, <a href="https://stdkmd.net/nrr/aaaba.htm">Near-repdigit numbers of the form AA...AABA</a>. %H A178429 Makoto Kamada, <a href="https://stdkmd.net/nrr/9/99949.htm#prime">Prime numbers of the form 99...9949</a>. %H A178429 <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>. %e A178429 10^4 - 51 = 9949 which is a prime number. %p A178429 A178429:=n->`if`(isprime(10^n-51), n, NULL): seq(A178429(n), n=1..1000); # _Wesley Ivan Hurt_, Nov 26 2014 %t A178429 m = 1000; For[n = 1, n < m, If[PrimeQ[10^n - 51], Print[n]]; n++ ] %o A178429 (PARI) is(n)=ispseudoprime(10^n-51) \\ _Charles R Greathouse IV_, Jun 06 2017 %Y A178429 Cf. A108330, A108328. %K A178429 more,nonn %O A178429 1,1 %A A178429 _Robert Price_, Dec 21 2010 %E A178429 a(10) = 50929 found by _Robert Price_ and added by _Patrick De Geest_, Nov 26 2014