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 A061983 #10 Dec 29 2024 00:41:57
%S A061983 0,0,1,11,54,202,671,2109,6460,19556,58893,176959,531218,1594062,
%T A061983 4782667,14348561,43046328,129139720,387419993,1162260915,3486783790,
%U A061983 10460352530,31381058871,94143178021,282429535604,847288608492,2541865827301,7625597483879,22876792453770
%N A061983 a(n) = 3^n - (3*n^2 + n + 2)/2.
%H A061983 Harry J. Smith, <a href="/A061983/b061983.txt">Table of n, a(n) for n = 0..200</a>
%H A061983 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,-12,10,-3).
%F A061983 G.f.: x^2*(1 + 5*x)/((1 - x)^3*(1 - 3*x)). - _Andrew Howroyd_, Dec 28 2024
%o A061983 (PARI) a(n) = { 3^n - (3*n^2 + n + 2)/2 } \\ _Harry J. Smith_, Jul 29 2009
%Y A061983 Column of A061980.
%K A061983 nonn
%O A061983 0,4
%A A061983 _Henry Bottomley_, May 24 2001