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 A077247 #16 Nov 12 2022 16:07:51
%S A077247 1,2,10,17,79,134,622,1055,4897,8306,38554,65393,303535,514838,
%T A077247 2389726,4053311,18814273,31911650,148124458,251239889,1166181391,
%U A077247 1978007462,9181326670,15572819807,72284431969,122604550994,569094129082
%N A077247 Combined Diophantine Chebyshev sequences A077245 and A077243.
%C A077247 -5*a(n)^2 + 3*b(n)^2 = 7, with the companion sequence b(n)= A077248(n).
%C A077247 In addition to the comment above: 3*b(n)^2 = 5*a(n-2)*a(n+2) + 112, where b(n) = (a(n+2) - a(n-2))/6 = A077248(n), n >= 2. - _Klaus Purath_, Aug 12 2021
%H A077247 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>
%H A077247 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,8,0,-1).
%F A077247 a(2*k)= A077245(k) and a(2*k+1)= A077243(k), k>=0.
%F A077247 G.f.: (1+x)*(1+x+x^2)/(1-8*x^2+x^4).
%F A077247 From _Klaus Purath_, Aug 12 2021: (Start)
%F A077247 a(n) = 8*a(n-2) - a(n-4), n >= 4.
%F A077247 a(n) = (a(n-2)*a(n-4) - 168)/a(n-6), n >= 6.
%F A077247 a(n) = (a(n-1)*a(n-2) - 15/2 - 9/2*(-1)^n)/a(n-3), n >= 3. (End)
%e A077247 5*a(1)^2 + 7 = 5*4 + 7 = 27 = 3*3^2 = 3*A077248(1)^2.
%t A077247 LinearRecurrence[{0,8,0,-1},{1,2,10,17},30] (* _Harvey P. Dale_, Nov 12 2022 *)
%Y A077247 Cf. A077243, A077245, A077248.
%K A077247 nonn,easy
%O A077247 0,2
%A A077247 _Wolfdieter Lang_, Nov 08 2002