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 A209974 #11 Jun 28 2021 08:54:41 %S A209974 0,0,3,5,9,13,19,25,33,39,51,61,69,81,99,107,123,139,157,175,191,203, %T A209974 233,255,271,291,327,345,369,397,421,451,483,503,551,575,599,635,689, %U A209974 713,745,785,821,863,903,927,993,1039,1071,1113,1173 %N A209974 a(n) = A209973(n)/4. %C A209974 For a guide to related sequences, see A210000. %F A209974 Apparently, a(n) = a(n-1) + 2*A126246(n) - A000010(n) for n >= 2. - _Pontus von Brömssen_, Jun 28 2021 %t A209974 (See the Mathematica section at A210000.) %Y A209974 Cf. A210000. %Y A209974 Cf. A000010, A126246. %K A209974 nonn %O A209974 0,3 %A A209974 _Clark Kimberling_, Mar 16 2012