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 A198647 #24 Jun 02 2025 05:24:27
%S A198647 2,20,146,1028,7202,50420,352946,2470628,17294402,121060820,847425746,
%T A198647 5931980228,41523861602,290667031220,2034669218546,14242684529828,
%U A198647 99698791708802,697891541961620,4885240793731346,34196685556119428
%N A198647 3*7^n-1.
%H A198647 Vincenzo Librandi, <a href="/A198647/b198647.txt">Table of n, a(n) for n = 0..1000</a>
%H A198647 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (8,-7).
%F A198647 a(n) = 7*a(n-1)+6, a(0)=2.
%F A198647 G.f.: ( 2+4*x ) / ( (7*x-1)*(x-1) ). - _R. J. Mathar_, Oct 30 2011
%F A198647 a(n) = 8*a(n-1) - 7*a(n-2). - _Harvey P. Dale_, Jan 27 2012
%t A198647 3*7^Range[0,20]-1 (* or *) LinearRecurrence[{8,-7},{2,20},20] (* _Harvey P. Dale_, Jan 27 2012 *)
%o A198647 (Magma) [3*7^n-1: n in [0..30]]
%o A198647 (PARI) a(n)=3*7^n-1 \\ _Charles R Greathouse IV_, Nov 21 2011
%K A198647 nonn,easy,less
%O A198647 0,1
%A A198647 _Vincenzo Librandi_, Oct 28 2011