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 A268356 #12 Jun 13 2017 10:34:49 %S A268356 0,1,2,5,25,85,92,97,649,2017,2978,3577,4985,17978,21365,66002,95305, %T A268356 142199 %N A268356 Numbers n such that 8*9^n - 1 is prime. %C A268356 a(19) > 2*10^5. %t A268356 Select[Range[0, 200000], PrimeQ[8*9^# - 1] &] (* _Robert Price_, Feb 02 2016 *) %o A268356 (PARI) is(n)=ispseudoprime(8*9^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017 %Y A268356 Cf. A056799, A198966. %K A268356 nonn,more %O A268356 1,3 %A A268356 _Robert Price_, Feb 02 2016