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 A387245 #17 Aug 28 2025 19:37:04
%S A387245 1,5,9,24,1400,8915
%N A387245 Numbers k such that (the concatenation of the first k positive even numbers) + 1 is prime.
%C A387245 a(6) = 8915 corresponds to a 39024-digit probable prime. a(7) > 15000.
%C A387245 The corresponding primes are a subsequence of A210734. - _Michael S. Branicky_, Aug 24 2025
%F A387245 {k | A019520(k) + 1 is prime}. - _Michael S. Branicky_, Aug 24 2025
%e A387245 5 is a term since 246810 + 1 = 246811 is prime.
%Y A387245 Cf. A019520, A069048, A210734.
%K A387245 base,more,nonn,new
%O A387245 1,2
%A A387245 _Shyam Sunder Gupta_, Aug 24 2025