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 A143460 #12 Oct 11 2023 19:21:08
%S A143460 1,4,7,10,13,16,19,22,25,28,31,43,64,94,133,181,238,304,379,463,556,
%T A143460 685,877,1159,1558,2101,2815,3727,4864,6253,7921,9976,12607,16084,
%U A143460 20758,27061,35506,46687,61279,80038,103801,133729,171550,219802,282076
%N A143460 Expansion of 1/(x^k*(1-x-3*x^(k+1))) for k=9.
%C A143460 a(n) is also the number of length n quaternary words with at least 9 0-digits between any other digits.
%H A143460 Vincenzo Librandi, <a href="/A143460/b143460.txt">Table of n, a(n) for n = 0..1000</a>
%H A143460 <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,0,0,0,0,0,0,3).
%F A143460 G.f.: 1/(x^9*(1-x-3*x^10)).
%p A143460 a := proc(k::nonnegint) local n,i,j; if k=0 then unapply (4^n,n) else unapply ((Matrix(k+1, (i,j)-> if (i=j-1) or j=1 and i=1 then 1 elif j=1 and i=k+1 then 3 else 0 fi)^(n+k))[1,1], n) fi end(9): seq (a(n), n=0..61);
%t A143460 Series[1/(1-x-3*x^10), {x, 0, 61}] // CoefficientList[#, x]& // Drop[#, 9]& (* _Jean-François Alcover_, Feb 13 2014 *)
%Y A143460 9th column of A143461.
%K A143460 nonn,easy
%O A143460 0,2
%A A143460 _Alois P. Heinz_, Aug 16 2008