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 A026381 #11 Dec 31 2021 18:02:17
%S A026381 1,4,11,17,30,39,58,70,95,110,141,159,196,217,260,284,333,360,415,445,
%T A026381 506,539,606,642,715,754,833,875,960,1005,1096,1144,1241,1292,1395,
%U A026381 1449,1558,1615,1730,1790,1911,1974,2101,2167,2300
%N A026381 T(n,n-2), where T is the array in A026374.
%H A026381 Reinhard Zumkeller, <a href="/A026381/b026381.txt">Table of n, a(n) for n = 2..1000</a>
%H A026381 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A026381 G.f.: z^2*(1+3z+5z^2)/[(1-z)^3*(1+z)^2]. - _Emeric Deutsch_, Jan 25 2004
%t A026381 Drop[CoefficientList[Series[z^2(1+3z+5z^2)/((1-z)^3(1+z)^2),{z,0,50}],z],2] (* or *) LinearRecurrence[{1,2,-2,-1,1},{1,4,11,17,30},50] (* _Harvey P. Dale_, Dec 31 2021 *)
%o A026381 (Haskell)
%o A026381 a026381 = flip a026374 2 -- _Reinhard Zumkeller_, Feb 22 2014
%K A026381 nonn
%O A026381 2,2
%A A026381 _Clark Kimberling_