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 A077238 #25 Mar 14 2024 13:03:44
%S A077238 4,5,11,16,40,59,149,220,556,821,2075,3064,7744,11435,28901,42676,
%T A077238 107860,159269,402539,594400,1502296,2218331,5606645,8278924,20924284,
%U A077238 30897365,78090491,115310536,291437680,430344779,1087660229,1606068580,4059203236,5993929541
%N A077238 Combined Diophantine Chebyshev sequences A077236 and A077235.
%C A077238 a(n)^2 - 3*b(n)^2 = 13, with the companion sequence b(n)= A077237(n).
%C A077238 Positive values of x (or y) satisfying x^2 - 4xy + y^2 + 39 = 0. - _Colin Barker_, Feb 06 2014
%C A077238 Positive values of x (or y) satisfying x^2 - 14xy + y^2 + 624 = 0. - _Colin Barker_, Feb 16 2014
%H A077238 Vincenzo Librandi, <a href="/A077238/b077238.txt">Table of n, a(n) for n = 0..1000</a>
%H A077238 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%H A077238 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,0,-1).
%F A077238 a(2*k)= A077236(k) and a(2*k+1)= A077235(k), k>=0.
%F A077238 G.f.: (1-x)*(4+9*x+4*x^2)/(1-4*x^2+x^4).
%F A077238 a(n) = 4*a(n-2)-a(n-4). - _Colin Barker_, Feb 06 2014
%e A077238 11 = a(2) = sqrt(3*A077237(2)^2 + 13) = sqrt(3*6^2 + 13)= sqrt(121) = 11.
%t A077238 CoefficientList[Series[(1 - x) (4 + 9 x + 4 x^2)/(1 - 4 x^2 + x^4), {x, 0, 40}], x] (* _Vincenzo Librandi_, Feb 07 2014 *)
%t A077238 LinearRecurrence[{0,4,0,-1},{4,5,11,16},40] (* _Harvey P. Dale_, Oct 23 2015 *)
%K A077238 nonn,easy
%O A077238 0,1
%A A077238 _Wolfdieter Lang_, Nov 08 2002
%E A077238 More terms from _Colin Barker_, Feb 06 2014