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 A174474 #22 Sep 08 2022 08:45:51
%S A174474 0,0,-1,3,0,8,3,15,8,24,15,35,24,48,35,63,48,80,63,99,80,120,99,143,
%T A174474 120,168,143,195,168,224,195,255,224,288,255,323,288,360,323,399,360,
%U A174474 440,399,483,440,528,483,575,528,624,575
%N A174474 a(n) = (2*n^2 - 2*n - 3)/8 + 3*(-1)^n*(1-2*n)/8.
%C A174474 First differences are (-1)^n*A022998(n).
%H A174474 Vincenzo Librandi, <a href="/A174474/b174474.txt">Table of n, a(n) for n = 0..1000</a>
%H A174474 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A174474 Bisections: a(2n) = A067998(n). a(2n+1) = A005563(n).
%F A174474 a(2n) + a(2n+1) = A001105(n).
%F A174474 a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) - a(n-4) + a(n-5).
%F A174474 G.f.: x^2*(1 - 4*x + x^2) / ( (1+x)^2*(x-1)^3 ).
%t A174474 LinearRecurrence[{1,2,-2,-1,1},{0,0,-1,3,0},60] (* _Harvey P. Dale_, Jun 01 2015 *)
%o A174474 (Magma) [(2*n^2-2*n-3)/8+3*(-1)^n*(1-2*n)/8: n in [0..60]]; // _Vincenzo Librandi_, Aug 04 2011
%K A174474 sign,easy
%O A174474 0,4
%A A174474 _Paul Curtz_, Nov 28 2010