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 A075610 #5 Jan 08 2019 09:12:41 %S A075610 1,2,5,7,11,13,3,19,17,29,23,31,41,37,43,47,53,59,61,67,71,73,79,83, %T A075610 97,89,103,101,109,107,113,127,131,137,139,149,151,167,157,173,163, %U A075610 179,181,191,193,197,199,223,227,211,233,229,239,241,251,269,263,271,257,277 %N A075610 a(1) = 1, a(n) = smallest prime number not occurring earlier such that the concatenation a(n-1) and a(n) is a composite number. %Y A075610 Cf. A075607, A075608, A075609. %K A075610 base,nonn %O A075610 1,2 %A A075610 _Amarnath Murthy_, Sep 28 2002 %E A075610 More terms from _Michel ten Voorde_ Jun 23 2003