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 A130980 #24 Jan 30 2020 21:29:16
%S A130980 1,9,153,3177,73017,1785609,45543897,1197639081,32231934585,
%T A130980 883404542025,24570973169433,691759954058985,19674867844155321,
%U A130980 564462038150345097,16315646312285498457,474680922491822688297
%N A130980 G.f.: 16/(7 + 9*sqrt(1 - 32*x)).
%C A130980 Number of walks of length 2n on the 9-regular tree beginning and ending at some fixed vertex. Hankel transform is A135320. - _Philippe Deléham_, Feb 25 2009
%H A130980 G. C. Greubel, <a href="/A130980/b130980.txt">Table of n, a(n) for n = 0..660</a>
%F A130980 a(n) = Sum_{k=0..n} A039599(n,k)*8^(n-k). - _Philippe Deléham_, Aug 25 2007
%F A130980 a(n) ~ 72/49*32^n/(sqrt(Pi)*n^(3/2)). - _Vaclav Kotesovec_, Jun 29 2013
%F A130980 D-finite with recurrence: n*a(n) +(-113*n+48)*a(n-1) +1296*(2*n-3)*a(n-2)=0. - _R. J. Mathar_, Jan 20 2020
%t A130980 CoefficientList[Series[16/(7+9*Sqrt[1-32*x]),{x,0,30}],x] (* _Harvey P. Dale_, Feb 21 2013 *)
%o A130980 (PARI) Vec(16/(7 + 9*sqrt(1-32*x)) + O(x^50)) \\ _G. C. Greubel_, Jan 28 2017
%Y A130980 Column k=9 of A183135.
%K A130980 nonn
%O A130980 0,2
%A A130980 _Philippe Deléham_, Aug 23 2007
%E A130980 More terms from _Olivier Gérard_, Sep 22 2007