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 A084518 #11 Jul 29 2017 12:43:17
%S A084518 1,2,5,18,65,238,877,3234,11929,44006,162341,598890,2209361,8150542,
%T A084518 30068125,110924178,409209865,1509614198,5569110677,20544980154,
%U A084518 75792390209,279605352286,1031490797581,3805267877730,14037995932921
%N A084518 Partial sums of A084519. Positions of ones in the first differences of A084516.
%H A084518 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3, 2, 2).
%F A084518 Empirical G.f.: x*(1-2*x-2*x^2)/((1-x)*(1-3*x-2*x^2-2*x^3)). [_Colin Barker_, Apr 17 2012]
%t A084518 Accumulate[LinearRecurrence[{3,2,2},{1,1,3},30]] (* _Harvey P. Dale_, Jul 20 2013 *)
%K A084518 nonn
%O A084518 1,2
%A A084518 _Antti Karttunen_, Jun 02 2003