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 A099235 #18 Jun 27 2025 23:33:21
%S A099235 1,1,5,15,45,140,431,1326,4085,12580,38740,119305,367411,1131476,
%T A099235 3484490,10730820,33046585,101770120,313410816,965178576,2972359720,
%U A099235 9153665985,28189589705,86812537085,267347509271,823322219501
%N A099235 A quadrisection of 1/(1-x-x^5).
%C A099235 A row of A099233.
%C A099235 The number of ways to place non-overlapping Young diagrams of shape (2,1,1,1) on an 7 by n rectangle. - _Per Alexandersson_, Jun 23 2025
%H A099235 Harvey P. Dale, <a href="/A099235/b099235.txt">Table of n, a(n) for n = 0..1000</a>
%H A099235 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,4,6,4,1).
%F A099235 G.f.: 1/(1-x*(1+x)^4).
%F A099235 a(n) = Sum_{k=0..n} binomial(4(n-k), k).
%F A099235 a(n) = a(n-1) + 4*a(n-2) + 6*a(n-3) + 4*a(n-4) + a(n-5).
%F A099235 a(n) = A003520(4n).
%t A099235 Take[CoefficientList[Series[1/(1-x-x^5),{x,0,100}],x],{1,-1,4}] (* or *) LinearRecurrence[{1,4,6,4,1},{1,1,5,15,45},30] (* _Harvey P. Dale_, Mar 06 2015 *)
%Y A099235 Cf. A003520, A099233.
%K A099235 easy,nonn
%O A099235 0,3
%A A099235 _Paul Barry_, Oct 08 2004