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 A161208 #6 Mar 02 2020 00:52:46 %S A161208 0,1,3,6,10,15,21,28,34,40,49,61,76,91,105,120,130,136,145,158,175, %T A161208 196,221,249,276,298,322,354,395,435,469,502,520,526,535,548,565,586, %U A161208 611,640,669,696,729,774,831,894,955,1015,1066,1096,1120,1155,1202,1261,1332 %N A161208 a(n) = (A161206(n+1)-1)/2. %Y A161208 Cf. A161206, A161207, A161209. %K A161208 nonn %O A161208 0,3 %A A161208 _Omar E. Pol_, Jun 08 2009 %E A161208 More terms from _Jinyuan Wang_, Mar 01 2020