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 A026411 #8 Sep 27 2019 02:50:52 %S A026411 4,6,10,12,15,19,23,25,30,36,43,45,51,54,66,67,77,87,90,99,100,124, %T A026411 125,135,139,145,158,178,180,196,197,201,225,241,252,256,258,283,302, %U A026411 303,321,327,350,383,390,405,407,426,447,459,477,520,523,542,568,569,586,611,614,615 %N A026411 Position of the second n in A026409. %K A026411 nonn %O A026411 2,1 %A A026411 _Clark Kimberling_ %E A026411 More terms from _Sean A. Irvine_, Sep 26 2019