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 A247841 #26 Jan 28 2025 11:50:51
%S A247841 0,64,576,4672,37440,299584,2396736,19173952,153391680,1227133504,
%T A247841 9817068096,78536544832,628292358720,5026338869824,40210710958656,
%U A247841 321685687669312,2573485501354560,20587884010836544,164703072086692416,1317624576693539392
%N A247841 a(n) = Sum_{k=2..n} 8^k.
%H A247841 Vincenzo Librandi, <a href="/A247841/b247841.txt">Table of n, a(n) for n = 1..200</a>
%H A247841 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (9,-8).
%F A247841 G.f.: 64*x^2/((1-x)*(1-8*x)).
%F A247841 a(n) = a(n-1) + 8^n.
%F A247841 a(n) = (8^(n+1) - 64)/7.
%F A247841 a(n) = 9*a(n-1) - 8*a(n-2).
%F A247841 a(n) = A052379(n) - 8. - _Michel Marcus_, Sep 25 2014
%t A247841 RecurrenceTable[{a[1] == 0, a[n] == a[n-1] + 8^n}, a, {n, 30}] (* or *) CoefficientList[Series[64 x / ((1 - x) (1 - 8 x)), {x, 0, 30}], x]
%t A247841 LinearRecurrence[{9,-8},{0,64},30] (* _Harvey P. Dale_, May 01 2018 *)
%o A247841 (Magma) [0] cat [&+[8^k: k in [2..n]]: n in [2..30]];
%o A247841 (Magma) [(8^(n+1)-64)/7: n in [1..30]];
%Y A247841 Cf. similar sequences listed in A247817.
%Y A247841 Cf. A052379.
%K A247841 nonn,easy
%O A247841 1,2
%A A247841 _Vincenzo Librandi_, Sep 25 2014