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 A190456 #5 Mar 30 2012 18:57:28 %S A190456 8,21,42,55,76,97,110,131,144,152,165,186,199,220,241,254,275,288,309, %T A190456 330,343,364,377,385,398,419,432,453,474,487,508,521,542,563,576,597, %U A190456 618,631,652,665,686,707,720,741,754,762,775,796,809,830,851,864,885,898,919 %N A190456 Positions of 4 in A190451. %C A190456 See A190451. %t A190456 (See A190451.) %Y A190456 Cf. A190451. %K A190456 nonn %O A190456 1,1 %A A190456 _Clark Kimberling_, May 10 2011