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 A084860 #14 Feb 06 2022 06:56:04
%S A084860 1,2,6,15,36,84,192,432,960,2112,4608,9984,21504,46080,98304,208896,
%T A084860 442368,933888,1966080,4128768,8650752,18087936,37748736,78643200,
%U A084860 163577856,339738624,704643072,1459617792,3019898880,6241124352
%N A084860 Expansion of (1 - 2x + 2x^2 - x^3)/(1 - 2x)^2.
%C A084860 Partial sums are A084858. Partial sums of A084860.
%H A084860 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4).
%F A084860 a(0)=1, a(n+1) = 3*2^(n-2)*(n+3) - 0^n/4.
%F A084860 Equals binomial transform of nonzero terms of A026741: (1, 1, 3, 2, 5, 3, 7, 4, ...). - _Gary W. Adamson_, Apr 25 2008
%F A084860 Equals row sums of triangle A139633. - _Gary W. Adamson_, Apr 27 2008
%t A084860 CoefficientList[Series[(1-2x+2x^2-x^3)/(1-2x)^2,{x,0,50}],x] (* _Harvey P. Dale_, Mar 30 2011 *)
%Y A084860 Cf. A026741.
%Y A084860 Cf. A139633.
%K A084860 easy,nonn
%O A084860 0,2
%A A084860 _Paul Barry_, Jun 12 2003