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 A139790 #20 Sep 08 2022 08:45:33
%S A139790 1,2,3,5,7,9,7,-7,-57,-199,-569,-1479,-3641,-8647,-20025,-45511,
%T A139790 -101945,-225735,-495161,-1077703,-2330169,-5009863,-10718777,
%U A139790 -22835655,-48467513,-102527431,-216239673,-454848967,-954437177,-1998352839,-4175662649,-8709239239
%N A139790 a(n) = (5*2^(n+2) - 3*n*2^n - 2*(-1)^n) / 18.
%C A139790 Binomial transform of 1,1,0,1,-2,3,-8,13,-30,... (see A113954 and A103196). - _R. J. Mathar_, Feb 11 2010
%H A139790 Vincenzo Librandi, <a href="/A139790/b139790.txt">Table of n, a(n) for n = 0..1000</a>
%H A139790 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,0,-4)
%F A139790 a(n+1) - 2*a(n) = -A001045(n).
%F A139790 G.f.: (1 - x - 3*x^2)/((1+x)*(1-2*x)^2).
%F A139790 a(n) = 3*a(n-1) - 4*a(n-3).
%t A139790 LinearRecurrence[{3,0,-4},{1,2,3},40] (* _Harvey P. Dale_, May 27 2018 *)
%o A139790 (Magma) [(5*2^(n+2)-3*n*2^n-2*(-1)^n) / 18: n in [0..35]]; // _Vincenzo Librandi_, Aug 09 2011
%Y A139790 Cf. A136298, A136299.
%K A139790 sign,easy
%O A139790 0,2
%A A139790 _Paul Curtz_, May 21 2008
%E A139790 Definition replaced with closed formula by _R. J. Mathar_, Feb 11 2010