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 A103201 #17 Sep 08 2022 08:45:16
%S A103201 11,19,89,151,701,1189,5519,9361,43451,73699,342089,580231,2693261,
%T A103201 4568149,21203999,35964961,166938731,283151539,1314305849,2229247351,
%U A103201 10347508061,17550827269,81465758639,138177370801,641378561051
%N A103201 a(1) = 11, a(2) = 19, a(3) = 89, a(4) = 151; for n >= 5, a(n) = sqrt(a(n-4)^2 + 60*a(n-2)^2 + 4*a(n-2)*sqrt(210 + 15*a(n-4)^2)).
%D A103201 K. S. Bhanu (bhanu_105(AT)yahoo.com) and M. N. Deshpande, An interesting sequence of quadruples and related open problems, Institute of Sciences, Nagpur, India, Preprint, 2005.
%H A103201 G. C. Greubel, <a href="/A103201/b103201.txt">Table of n, a(n) for n = 1..1000</a>
%H A103201 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,8,0,-1).
%F A103201 G.f.: x*(11 + 19*x + x^2 - x^3)/(1 - 8*x^2 + x^4). - _Georg Fischer_, May 24 2019
%p A103201 b[1]:=11:b[2]:=19:b[3]:=89:b[4]:=151: for n from 5 to 28 do b[n]:=sqrt(b[n-4]^2+60*b[n-2]^2+4*b[n-2]*sqrt(210+15*b[n-4]^2)) od:seq(b[n],n=1..28); # _Emeric Deutsch_, Apr 13 2005
%t A103201 LinearRecurrence[{0, 8, 0, -1}, {11, 19, 89, 151}, 30] (* _Georg Fischer_, May 24 2019 *)
%o A103201 (PARI) my(x='x+O('x^30)); Vec(x*(11+19*x+x^2-x^3)/(1-8*x^2+x^4)) \\ _G. C. Greubel_, May 24 2019
%o A103201 (Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( x*(11+19*x+x^2-x^3)/(1-8*x^2+x^4) )); // _G. C. Greubel_, May 24 2019
%o A103201 (Sage) a=(x*(11+19*x+x^2-x^3)/(1-8*x^2+x^4)).series(x, 30).coefficients(x, sparse=False); a[1:] # _G. C. Greubel_, May 24 2019
%o A103201 (GAP) a:=[11,19,89,151];; for n in [5..30] do a[n]:=8*a[n-2]-a[n-4]; od; a; # _G. C. Greubel_, May 24 2019
%Y A103201 This is the sequence b(n) defined in A103200. Bhanu and Deshpande ask for a proof that the terms of the sequence are always integers.
%Y A103201 Cf. A103200.
%K A103201 nonn
%O A103201 1,1
%A A103201 K. S. Bhanu and M. N. Deshpande, Mar 24 2005
%E A103201 More terms from _Pierre CAMI_ and _Emeric Deutsch_, Apr 13 2005