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 A004142 #12 Oct 24 2023 20:29:23
%S A004142 0,1,10,57,260,1055,3990,14413,50440,172539,580250,1926089,6328140,
%T A004142 20619703,66732190,214742085,687698960,2193154547,6968850210,
%U A004142 22073006401,69714716500,219623377071,690291036710
%N A004142 a(n) = n*(3^n - 2^n).
%H A004142 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (10,-37,60,-36).
%F A004142 From _R. J. Mathar_, Feb 10 2022: (Start)
%F A004142 G.f.: -x*(-1+6*x^2) / ( (3*x-1)^2*(2*x-1)^2 ).
%F A004142 a(n) = A036290(n) - A036289(n). (End)
%t A004142 Table[n(3^n-2^n),{n,0,30}] (* or *) LinearRecurrence[{10,-37,60,-36},{0,1,10,57},30] (* _Harvey P. Dale_, Sep 04 2023 *)
%Y A004142 Equals n * A001047(n).
%K A004142 nonn,easy
%O A004142 0,3
%A A004142 _N. J. A. Sloane_