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 A146884 #13 Mar 20 2024 16:03:05
%S A146884 7,49,301,1813,10885,65317,391909,2351461,14108773,84652645,507915877,
%T A146884 3047495269,18284971621,109709829733,658258978405,3949553870437,
%U A146884 23697323222629,142183939335781,853103636014693,5118621816088165
%N A146884 a(n) = 7*Sum_{k=0..n} 6^k.
%H A146884 G. C. Greubel, <a href="/A146884/b146884.txt">Table of n, a(n) for n = 0..1000</a>
%H A146884 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7,-6).
%F A146884 From _G. C. Greubel_, Oct 12 2022: (Start)
%F A146884 a(n) = (7/5)*(6^(n+1) - 1).
%F A146884 a(n) = 7*A003464(n+1).
%F A146884 a(n) = 7*a(n-1) - 6*a(n-2).
%F A146884 G.f.: 7/((1-x)*(1-6*x)).
%F A146884 E.g.f.: (7/5)*(6*exp(6*x) - exp(x)). (End)
%t A146884 a[n_]:= Sum[7*6^m, {m,0,n}]; Table[a[n], {n,0,30}]
%t A146884 Accumulate[7*6^Range[0,20]] (* _Harvey P. Dale_, Dec 18 2021 *)
%o A146884 (Magma) [n le 2 select 7^n else 7*Self(n-1) -6*Self(n-2): n in [1..31]]; // _G. C. Greubel_, Oct 12 2022
%o A146884 (SageMath) [(7/5)*(6^(n+1)-1) for n in range(41)] # _G. C. Greubel_, Oct 12 2022
%Y A146884 Cf. A003464, A005843, A068156, A100774, A132583, A146882, A146883, A146885.
%K A146884 nonn,easy,less
%O A146884 0,1
%A A146884 _Roger L. Bagula_, Nov 02 2008