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 A369613 #14 Nov 30 2024 06:00:39 %S A369613 1,4,10,16,130,1900,5356,181960 %N A369613 Numbers k such that ceiling(10^k/7) is prime. %C A369613 a(n) == 4 (mod 6) for n > 1. %C A369613 1 and numbers k such that (10^k + 3)/7 is prime. %e A369613 4 is a term because ceiling(10^4/7) = 1429 is prime. %e A369613 . %e A369613 n | k = a(n) | ceiling(10^k/7) %e A369613 --+----------+----------------- %e A369613 1 | 1 | 2 %e A369613 2 | 4 | 1429 %e A369613 3 | 10 | 1428571429 %e A369613 4 | 16 | 1428571428571429 %Y A369613 Cf. A364644. %K A369613 nonn,more,hard %O A369613 1,2 %A A369613 _Jon E. Schoenfield_, Jan 27 2024 %E A369613 a(8) from _Jinyuan Wang_, Nov 30 2024