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 A296029 #29 Aug 07 2024 09:45:51 %S A296029 4,7,8,11,16,22,28,29,79,91,170,293,392,1898,2597,3641,4099,8236, %T A296029 11393,17969,18503,33322 %N A296029 Numbers k such that 10^k/8 - 1 is prime. %C A296029 Equivalently, numbers k such that 125*10^(k-3) - 1 is prime. %C A296029 Searched up to k = 20000. - _Michael B. Porter_, Dec 07 2017 %C A296029 Searched up to k = 40000. - _Michael S. Branicky_, Aug 07 2024 %e A296029 1249, 1249999, and 12499999 are prime, so 4, 7, and 8 are in the sequence. %t A296029 Select[Range[2000], PrimeQ[10^#/8 - 1] &] (* _Michael De Vlieger_, Dec 08 2017 *) %o A296029 (PARI) lista(nn) = for(n=4, nn, if(ispseudoprime(10^n/8 - 1), print1(n, ", "))) \\ _Iain Fox_, Dec 04 2017 %K A296029 nonn,more %O A296029 1,1 %A A296029 _Patrick A. Thomas_, Dec 03 2017 %E A296029 a(12), a(13), a(15), a(16) from _Jon E. Schoenfield_, Dec 03 2017 %E A296029 a(14) and a(17)-a(21) from _Michael B. Porter_, Dec 07 2017 %E A296029 a(22) from _Michael S. Branicky_, Aug 07 2024