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 A109617 #17 Aug 13 2025 19:48:56 %S A109617 2,3,4,7,77,337,397,566,615,822,1007,1017,1073,1351,1731,2635,6606, %T A109617 8513,10404 %N A109617 Numbers k such that (10's complement factorial of k) - 1 is prime. %e A109617 3 is a term because (10-3)*(10-2)*(10-1) - 1 = 503 is prime. %e A109617 77 is a term because (100-77)*..*(100-10)*(10-9)*..*(10-1) - 1 is prime. %Y A109617 Cf. A109616, A110396. %K A109617 nonn,base,hard,more %O A109617 1,1 %A A109617 _Jason Earls_, Aug 01 2005 %E A109617 a(9)-a(17) from _Jinyuan Wang_, Aug 09 2025 %E A109617 a(18)-a(19) from _Michael S. Branicky_, Aug 13 2025