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 A131607 #14 Jan 05 2020 21:43:05
%S A131607 1,4,9,23,57,139,336,811,1960,4732,11424,27580,66585,160752,388089,
%T A131607 936931,2261953,5460839,13183632,31828103,76839840,185507784,
%U A131607 447855408,1081218600,2610292609,6301803820,15213900249,36729604319,88673108889,214075822099,516824753088
%N A131607 Pell companion numbers A001333 without last digit.
%H A131607 Andrew Howroyd, <a href="/A131607/b131607.txt">Table of n, a(n) for n = 4..1000</a>
%F A131607 a(n) = floor(A001333(n) / 10). - _Andrew Howroyd_, Jan 02 2020
%F A131607 Conjectures from _Colin Barker_, Jan 03 2020: (Start)
%F A131607 G.f.: x^4*(1 + x - 2*x^2 + x^3 + x^4) / ((1 - x)*(1 + x^2)*(1 - 2*x - x^2)*(1 - x^2 + x^4)).
%F A131607 a(n) = 3*a(n-1) - a(n-2) - a(n-3) - a(n-6) + 3*a(n-7) - a(n-8) - a(n-9) for n>12.
%F A131607 (End)
%t A131607 Table[Floor[(((1 - Sqrt[2])^n + (1 + Sqrt[2])^n)/2)/10], {n, 4, 29}] (* _Metin Sariyar_, Jan 03 2020 *)
%o A131607 (PARI) a(n)={polcoef((1 - x) / (1 - 2*x - x^2) + O(x*x^n), n)\10} \\ _Andrew Howroyd_, Jan 02 2020
%Y A131607 Cf. A001333, A131727.
%K A131607 nonn,base
%O A131607 4,2
%A A131607 _Paul Curtz_, Oct 02 2007
%E A131607 Offset changed and terms a(24) and beyond from _Andrew Howroyd_, Jan 02 2020