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 A261801 #16 Aug 21 2024 09:43:10
%S A261801 1,9,126,1704,22986,310086,4183260,56435004,761346207,10271072557,
%T A261801 138563678736,1869317246556,25218347263608,340212470558832,
%U A261801 4589695110222504,61918074814238448,835316485437693186,11268981358631127288,152026139882340589466
%N A261801 Number of 9-compositions of n: matrices with 9 rows of nonnegative integers with positive column sums and total element sum n.
%C A261801 Also the number of compositions of n where each part i is marked with a word of length i over a nonary alphabet whose letters appear in alphabetical order.
%H A261801 Alois P. Heinz, <a href="/A261801/b261801.txt">Table of n, a(n) for n = 0..880</a>
%H A261801 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (18, -72, 168, -252, 252, -168, 72, -18, 2).
%F A261801 G.f.: (1-x)^9/(2*(1-x)^9-1).
%F A261801 a(n) = A261780(n,9).
%F A261801 a(n) = Sum_{k>=0} (1/2)^(k+1) * binomial(n-1+9*k,n). - _Seiichi Manyama_, Aug 06 2024
%p A261801 a:= proc(n) option remember; `if`(n=0, 1,
%p A261801 add(a(n-j)*binomial(j+8, 8), j=1..n))
%p A261801 end:
%p A261801 seq(a(n), n=0..20);
%Y A261801 Column k=9 of A261780.
%K A261801 nonn,easy
%O A261801 0,2
%A A261801 _Alois P. Heinz_, Sep 01 2015