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 A100447 #3 Mar 30 2012 16:50:05 %S A100447 2,4,8,20,60,188,632,2192,7712,27596,99880,364724,1342184,4971068, %T A100447 18512792,69273668,260301176,981706832,3714566312,14096303344, %U A100447 53634713552,204560302844,781874936816,2994414645860,11488774559636 %N A100447 Bisection of A000031. %p A100447 with(numtheory):seq((1/(2*n+1))*add(phi(d)*2^((2*n+1)/d),d=divisors(2*n+1)),n=0..30); (C. Ronaldo) %Y A100447 Cf. A000031, A100446. Equals 2*A026119. %K A100447 nonn,easy %O A100447 0,1 %A A100447 _N. J. A. Sloane_, Nov 21 2004 %E A100447 More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 19 2005