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 A111216 #30 Mar 19 2024 11:48:51
%S A111216 1,30,929,28769,890910,27589441,854381761,26458245150,819351217889,
%T A111216 25373429509409,785756963573790,24333092441278081,753540108716046721,
%U A111216 23335410277756170270,722644178501725231649,22378634123275726010849,693015013643045781104670
%N A111216 a(n) = 31*a(n-1)-a(n-2).
%C A111216 Take 31 numbers consisting of 29 ones together with any two successive terms from this sequence. This set has the property that the sum of their squares is 31 times their product. (Guy)
%C A111216 Positive values of x (or y) satisfying x^2 - 31xy + y^2 + 29 = 0. - _Colin Barker_, Feb 24 2014
%H A111216 Vincenzo Librandi, <a href="/A111216/b111216.txt">Table of n, a(n) for n = 0..200</a>
%H A111216 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H A111216 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (31,-1).
%F A111216 G.f.: (1-x)/(1-31*x+x^2). [_Philippe Deléham_, Nov 18 2008]
%F A111216 a(n) = A200442(n) - A200442(n-1). - _R. J. Mathar_, Feb 13 2016
%t A111216 CoefficientList[Series[(1 - x)/(1 - 31 x + x^2), {x, 0, 40}], x] (* _Vincenzo Librandi_, Feb 26 2014 *)
%o A111216 (PARI) Vec((1-x)/(1-31*x+x^2) + O(x^100)) \\ _Colin Barker_, Feb 24 2014
%o A111216 (Magma) I:=[1,30]; [n le 2 select I[n] else 31*Self(n-1)-Self(n-2): n in [1..20]]; // _Vincenzo Librandi_, Feb 26 2014
%Y A111216 Cf. A049685.
%Y A111216 Cf. similar sequences listed in A238379.
%K A111216 nonn,easy
%O A111216 0,2
%A A111216 _N. J. A. Sloane_, following a suggestion from _R. K. Guy_, Oct 26 2005