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 A108924 #10 Apr 18 2025 22:22:30
%S A108924 1,2,10,34,146,562,2290,9074,36466,145522,582770,2329714,9321586,
%T A108924 37280882,149134450,596515954,2386107506,9544342642,38177545330,
%U A108924 152709831794,610840026226,2443358706802,9773437623410,39093744901234
%N A108924 J(n)^2+J(n+1)^2, with J(n) the Jacobsthal number A001045(n).
%H A108924 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,6,-8).
%F A108924 G.f.: (1-x-2x^2)/((1-x)(1-4x)(1+2x)); a(n)=3a(n-1)+6a(n-2)-8a(n-3); a(n)=(5/9)4^n+(2/9)(-2)^n+2/9.
%F A108924 a(0)=1, a(1)=2, a(2)=10, a(n)=3*a(n-1)+6*a(n-2)-8*a(n-3). - _Harvey P. Dale_, Apr 11 2013
%t A108924 Total/@Partition[LinearRecurrence[{1,2},{0,1},40]^2,2,1] (* or *) LinearRecurrence[ {3,6,-8},{1,2,10},40] (* _Harvey P. Dale_, Apr 11 2013 *)
%o A108924 (Python)
%o A108924 def A108924(n): return (((1<<n)|1)//3)**2+(((1<<n+1)|1)//3)**2 # _Chai Wah Wu_, Apr 18 2025
%K A108924 easy,nonn
%O A108924 0,2
%A A108924 _Paul Barry_, Jul 17 2005