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 A173674 #26 Jul 01 2019 03:24:11
%S A173674 0,1,1,1,1,1,2,2,3,4,5,7,10,13,18,25,35,48,66,91,125,173,238,329,454,
%T A173674 626,864,1193,1646,2272,3136,4329,5975,8247,11383,15711,21686,29932,
%U A173674 41315,57026,78711,108643,149958,206983,285694,394337,544295,751278,1036972
%N A173674 a(n) = ceiling(A003269(n)/2).
%H A173674 <a href="/index/Rec#order_19">Index entries for linear recurrences with constant coefficients</a>, signature (1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1, 0, 0, -1).
%F A173674 a(n) = A003269(n) - floor(A003269(n)/2):
%F A173674 a(n) = ceiling(A003269(n)/2).
%F A173674 a(n)= a(n-1) + a(n-4) + a(n-15) - a(n-16) - a(n-19). - _R. J. Mathar_, Sep 10 2016
%t A173674 b[0] = 0; b[1] = 1; b[2] = 1; b[3] = 1;
%t A173674 b[n_] := b[n] = b[n - 1] + b[n - 4]
%t A173674 Table[b[n] - Floor[b[n]/2], {n, 0, 30}]
%Y A173674 Cf. A003269.
%K A173674 nonn,easy
%O A173674 0,7
%A A173674 _Roger L. Bagula_, Nov 25 2010