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 A048773 #16 May 21 2021 14:25:21
%S A048773 1,11,32,84,209,511,1240,3000,7249,17507,42272,102060,246401,594871,
%T A048773 1436152,3467184,8370529,20208251,48787040,117782340,284351729,
%U A048773 686485807,1657323352,4001132520,9659588401,23320309331,56300207072,135920723484,328141654049
%N A048773 Partial sums of A048697.
%H A048773 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-1,-1).
%F A048773 a(n) = 2*a(n-1)+a(n-2)+9; a(0)=1, a(1)=11.
%F A048773 a(n) = (((10+(11/2)*sqrt(2))*(1+sqrt(2))^n - (10-(11/2)*sqrt(2))*(1-sqrt(2))^n)/ 2*sqrt(2))-9/2.
%F A048773 From _R. J. Mathar_, Nov 08 2012: (Start)
%F A048773 G.f.: ( 1+8*x ) / ( (x-1)*(x^2+2*x-1) ).
%F A048773 a(n) = A048739(n)+8*A048739(n-1). (End)
%F A048773 a(n) = 3*a(n-1)-a(n-2)-a(n-3). - _Wesley Ivan Hurt_, May 21 2021
%t A048773 Accumulate[LinearRecurrence[{2,1},{1,10},35]] (* _Harvey P. Dale_, Jul 26 2011 *)
%t A048773 LinearRecurrence[{3, -1, -1},{1, 11, 32},29] (* _Ray Chandler_, Aug 03 2015 *)
%Y A048773 Cf. A001333, A000129, A048696, A048697.
%K A048773 easy,nice,nonn
%O A048773 0,2
%A A048773 _Barry E. Williams_
%E A048773 More terms from _Harvey P. Dale_, Jul 26 2011