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 A228208 #27 Nov 03 2024 06:16:07
%S A228208 1,2,5,7,14,19,37,50,97,131,254,343,665,898,1741,2351,4558,6155,11933,
%T A228208 16114,31241,42187,81790,110447,214129,289154,560597,757015,1467662,
%U A228208 1981891,3842389,5188658,10059505,13584083,26336126,35563591,68948873,93106690
%N A228208 y-values in the solution to x^2 - 20*y^2 = 176.
%C A228208 Also y-values in the solution of x^2-5*y^2=44.
%H A228208 Vincenzo Librandi, <a href="/A228208/b228208.txt">Table of n, a(n) for n = 1..1000</a>
%H A228208 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,3,0,-1).
%F A228208 G.f.: x*(x+1)*(x^2+x+1) / ((x^2-x-1)*(x^2+x-1)).
%F A228208 a(n) = 3*a(n-2)-a(n-4).
%F A228208 Let h(n) = hypergeom([(1 - n)/2, (n + 1) mod 2 - n/2], [1 - n], -4) then a(n) = h(n-1) + h(n) for n > 2. - _Peter Luschny_, Sep 03 2019
%t A228208 CoefficientList[Series[(x + 1) (x^2 + x + 1) / ((x^2 - x - 1) (x^2 + x - 1)), {x, 0, 40}], x] (* _Vincenzo Librandi_, Aug 17 2013 *)
%o A228208 (PARI) Vec(x*(x+1)*(x^2+x+1)/((x^2-x-1)*(x^2+x-1)) + O(x^100))
%o A228208 (Magma) I:=[1,2,5,7,14]; [n le 4 select I[n] else 3*Self(n-2)-Self(n-4): n in [1..40]]; // _Vincenzo Librandi_, Aug 17 2013
%Y A228208 Cf. A228207, A054486 (bisection).
%K A228208 nonn,easy
%O A228208 1,2
%A A228208 _Colin Barker_, Aug 16 2013