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 A139782 #19 Sep 30 2024 01:52:41
%S A139782 1,2,5,15,46,139,417,1250,3749,11247,33742,101227,303681,911042,
%T A139782 2733125,8199375,24598126,73794379,221383137,664149410,1992448229,
%U A139782 5977344687,17932034062,53796102187,161388306561,484164919682,1452494759045
%N A139782 Binomial transform of A077947.
%H A139782 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,3).
%F A139782 a(n) = 3*a(n-1)-a(n-3)+3*a(n-4).
%F A139782 O.g.f.: -(1-x)^2/((3*x-1)*(x^2-x+1)). a(n) = (4*3^n+3*A010892(n)-A010892(n-1))/7. - _R. J. Mathar_, May 18 2008
%t A139782 LinearRecurrence[{3,0,-1,3},{1,2,5,15},30] (* _Harvey P. Dale_, Jan 12 2019 *)
%Y A139782 Cf. A010892, A077947, A133405, A122392.
%K A139782 nonn,easy
%O A139782 0,2
%A A139782 _Paul Curtz_, May 16 2008
%E A139782 More terms from _R. J. Mathar_, May 18 2008