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 A026955 #21 Dec 27 2024 17:09:19
%S A026955 1,3,8,25,60,175,400,1125,2500,6875,15000,40625,87500,234375,500000,
%T A026955 1328125,2812500,7421875,15625000,41015625,85937500,224609375,
%U A026955 468750000,1220703125,2539062500,6591796875,13671875000,35400390625
%N A026955 a(n) = Sum_{k=0..n} (k+1) * T(n,k), with T given by A026386.
%H A026955 Andrew Howroyd, <a href="/A026955/b026955.txt">Table of n, a(n) for n = 0..1000</a>
%H A026955 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,10,0,-25).
%F A026955 a(n) = (n + 2) * (7 - 3*(-1)^n) * 5^floor(n/2) / 10 for n > 0.
%F A026955 From _Colin Barker_, Oct 13 2012: (Start)
%F A026955 a(n) = 10*a(n-2) - 25*a(n-4) for n>4.
%F A026955 G.f.: (5*x^4-5*x^3-2*x^2+3*x+1)/(5*x^2-1)^2. (End)
%o A026955 (PARI) a(n) = if(n==0, 1, (n + 2) * (7 - 3*(-1)^n) * 5^floor(n/2) / 10) \\ _Andrew Howroyd_, Dec 27 2024
%Y A026955 Cf. A026386.
%K A026955 nonn,easy
%O A026955 0,2
%A A026955 _Clark Kimberling_