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 A027022 #15 Aug 03 2017 03:01:42
%S A027022 1,3,4,7,11,15,26,34,57,79,123,181,269,406,597,900,1332,1991,2968,
%T A027022 4414,6596,9805,14639,21792,32488,48418,72130,107532,160191,238776,
%U A027022 355785,530211,790156,1177431,1754739,2614807,3896754,5806922,8653577,12895791
%N A027022 a(n) = Sum_{k=floor((n+1)/2)..n} T(k,n-k); i.e., a(n) is n-th diagonal sum of left-justified array T given by A027011.
%H A027022 Vincenzo Librandi, <a href="/A027022/b027022.txt">Table of n, a(n) for n = 1..1000</a>
%F A027022 G.f.: x*(-x^4-3x^3+x^2+3x+1)/((1-x^2)*(1-2x^2-x^3+x^4)).
%t A027022 CoefficientList[Series[(-x^4 - 3 x^3 + x^2 + 3 x + 1) / ((1 - x^2) (1 - 2 x^2 - x^3 + x^4)), {x, 0, 60}], x] (* _Vincenzo Librandi_, Aug 03 2017 *)
%Y A027022 Cf. A027011.
%K A027022 nonn
%O A027022 1,2
%A A027022 _Clark Kimberling_