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 A254718 #23 Jul 14 2019 22:21:01 %S A254718 4,14,141,1141,11141,111413,1111413,11114137,111114137,1111141373, %T A254718 11111141373,111111413737,1111114137373,11111141373734, %U A254718 1111114137373402,11111141373734023,111111413737340234,11111114137373402349,111111114137373402349,1111111141373734023499 %N A254718 a(n) is the least semiprime having a(n-1) as a substring, a(1)=4. %H A254718 Jon E. Schoenfield, <a href="/A254718/b254718.txt">Table of n, a(n) for n = 1..71</a> %H A254718 Jon E. Schoenfield, <a href="/A254718/a254718.txt">Terms and factors for n = 1..71</a> %H A254718 Jon E. Schoenfield, <a href="/A254718/a254718_1.txt">Terms and factors for n = 1..71 and tentative additional terms through n=84</a> %e A254718 4=2*2, 14=2*7, 141=3*47, 1141=7*163, 11141=13*857, 111413=43*2591, 1111413=3*370471, 11114137=47*236471, 111114137=31*3584327, 1111141373=1051*1057223. %Y A254718 Cf. A001358, A030456. %K A254718 nonn,base %O A254718 1,1 %A A254718 _Zak Seidov_, Feb 06 2015 %E A254718 a(11)-a(20) from _Jon E. Schoenfield_, Feb 19 2015