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 A383912 #11 May 15 2025 06:57:52
%S A383912 1,9,45,177,621,2049,6525,20337,62541,190689,578205,1746897,5265261,
%T A383912 15844929,47633085,143095857,429680781,1289828769,3871059165,
%U A383912 11616323217,34855261101,104578366209,313760264445,941331124977,2824094038221,8472483441249,25417852976925
%N A383912 Expansion of (1+x) * (1+2*x)/((1-x) * (1-2*x) * (1-3*x)).
%H A383912 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (6,-11,6).
%F A383912 a(n) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3).
%F A383912 a(n) = Sum_{k=0..3} |Stirling1(3,k)| * Stirling2(k+n,3).
%F A383912 a(n) = 10*3^n - 3*2^(n+2) + 3.
%o A383912 (PARI) a(n) = 10*3^n-3*2^(n+2)+3;
%Y A383912 Column k=3 of A383818.
%Y A383912 Cf. A383910.
%K A383912 nonn,easy
%O A383912 0,2
%A A383912 _Seiichi Manyama_, May 15 2025