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 A101604 #19 Jun 01 2025 19:24:15
%S A101604 1,2,9,30,109,386,1377,4902,17461,62186,221481,788814,2809405,
%T A101604 10005842,35636337,126920694,452034757,1609945658,5733906489,
%U A101604 20421610782,72732645325,259041157538,922588763265,3285848604870,11702723341141
%N A101604 a(n) = 2*a(n-1) + 5*a(n-2) + 2*a(n-3).
%C A101604 Transform of 2^n under Riordan array A101603.
%H A101604 Harvey P. Dale, <a href="/A101604/b101604.txt">Table of n, a(n) for n = 0..1000</a>
%H A101604 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,5,2).
%F A101604 G.f.: 1/((1+x)*(1-3*x-2*x^2));
%F A101604 a(n) = (3/4 + sqrt(17)/4)^n*(1/4 + 7*sqrt(17)/68) + (1/4 - 7*sqrt(17)/68)*(3/4 - sqrt(17)/4)^n + (-1)^n/2;
%F A101604 a(n) = (A007483(n) + (-1)^n)/2. - _R. J. Mathar_, Sep 21 2012
%t A101604 LinearRecurrence[{2,5,2},{1,2,9},30] (* _Harvey P. Dale_, Jun 01 2025 *)
%Y A101604 Cf. A007483, A101603.
%K A101604 easy,nonn
%O A101604 0,2
%A A101604 _Paul Barry_, Dec 08 2004