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 A107583 #19 Sep 10 2024 11:03:51
%S A107583 1,0,3,18,69,228,711,2166,6537,19656,59019,177114,531405,1594284,
%T A107583 4782927,14348862,43046673,129140112,387420435,1162261410,3486784341,
%U A107583 10460353140,31381059543,94143178758,282429536409,847288609368,2541865828251,7625597484906,22876792454877
%N A107583 a(n) = 3^n - 3*n.
%C A107583 a(n) is the number k such that the number m with n 3's and k 1's has digit product = digit sum = 3^n.
%H A107583 Vincenzo Librandi, <a href="/A107583/b107583.txt">Table of n, a(n) for n = 0..1000</a>
%H A107583 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5,-7,3).
%F A107583 From _Elmo R. Oliveira_, Sep 09 2024: (Start)
%F A107583 G.f.: (1 - 5*x + 10*x^2)/((1 - 3*x)*(1 - x)^2).
%F A107583 E.g.f.: exp(x)*(exp(2*x) - 3*x).
%F A107583 a(n) = 5*a(n-1) - 7*a(n-2) + 3*a(n-3) for n > 2. (End)
%e A107583 Corresponding numbers m are 1, 3, 11133, 111111111111111111333, ...
%t A107583 Table[3^m-3*m, {m, 0, 20}]
%o A107583 (Magma) [3^n-3*n: n in [0..30]]; // _Vincenzo Librandi_, Oct 22 2011
%o A107583 (PARI) a(n)=3^n-3*n \\ _Charles R Greathouse IV_, Sep 08 2012
%Y A107583 Cf. A107584, A107585.
%K A107583 nonn,easy
%O A107583 0,3
%A A107583 _Zak Seidov_, May 16 2005
%E A107583 Corrected by _Charles R Greathouse IV_, Sep 08 2012