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 A048879 #37 Nov 01 2019 12:16:58
%S A048879 1,10,41,174,737,3122,13225,56022,237313,1005274,4258409,18038910,
%T A048879 76414049,323695106,1371194473,5808472998,24605086465,104228818858,
%U A048879 441520361897,1870310266446,7922761427681,33561355977170,142168185336361,602234097322614
%N A048879 Generalized Pellian with second term of 10.
%H A048879 Reinhard Zumkeller, <a href="/A048879/b048879.txt">Table of n, a(n) for n = 0..1000</a>
%H A048879 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H A048879 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,1)
%F A048879 a(n) = ((8+sqrt(5))*(2+sqrt(5))^n - (8-sqrt(5))*(2-sqrt(5))^n)2*sqrt(5).
%F A048879 From _Philippe Deléham_, Nov 03 2008: (Start)
%F A048879 a(n) = 4*a(n-1) + a(n-2); a(0)=1, a(1)=10.
%F A048879 G.f.: (1+6*x)/(1-4*x-x^2). (End)
%F A048879 For n >= 1, a(n) equals the denominator of the continued fraction [4, 4, ..., 4, 10] (with n copies of 4). The numerator of that continued fraction is a(n+1). - _ZhenShu Luan_, Aug 05 2019
%p A048879 with(combinat): a:=n->6*fibonacci(n-1,4)+fibonacci(n,4): seq(a(n), n=1..16); # _Zerinvary Lajos_, Apr 04 2008
%t A048879 LinearRecurrence[{4,1},{1,10},30] (* _Harvey P. Dale_, Jul 18 2011 *)
%o A048879 (Haskell)
%o A048879 a048879 n = a048879_list !! n
%o A048879 a048879_list = 1 : 10 : zipWith (+)
%o A048879 a048879_list (map (* 4) $ tail a048879_list)
%o A048879 -- _Reinhard Zumkeller_, Mar 03 2014
%Y A048879 Cf. A015448, A001077, A001076, A033887.
%K A048879 easy,nice,nonn
%O A048879 0,2
%A A048879 _Barry E. Williams_
%E A048879 More terms from _Harvey P. Dale_, Jul 18 2011