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 A307173 #7 Apr 01 2019 02:58:34 %S A307173 1,20,319,5084,81025,1291316,20580031,327989180,5227246849, %T A307173 83307960404,1327700119615,21159893953436,337230603135361, %U A307173 5374529756212340,85655245496262079,1365109398183980924,21756095125447432705,346732412608974942356,5525962506618151644991 %N A307173 Second class of all proper positive solutions y2(n) = a(n) of the Pell equation x^2 - 7*y^2 = 9. %C A307173 The corresponding x2 solutions are given in A307172. %C A307173 See A307172 for details. %H A307173 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a> %H A307173 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (16,-1). %F A307173 G.f.: x*(1 + 4*x)/(1 - 16*x + x^2). %F A307173 a(n) = -4*S(n, 16) + 65*S(n-1, 16) for n >= 1, with S(n,16) = A077412(n). %F A307173 a(n) = sqrt((A307172(n)^2 - 9)/7) for n >= 1. %Y A307173 Cf. A077421, A307168, A307169, A307172. %K A307173 nonn,easy %O A307173 1,2 %A A307173 _Wolfdieter Lang_, Mar 28 2019