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 A198694 #25 Apr 17 2024 08:34:18
%S A198694 6,27,111,447,1791,7167,28671,114687,458751,1835007,7340031,29360127,
%T A198694 117440511,469762047,1879048191,7516192767,30064771071,120259084287,
%U A198694 481036337151,1924145348607,7696581394431,30786325577727,123145302310911,492581209243647,1970324836974591
%N A198694 a(n) = 7*4^n-1.
%H A198694 Vincenzo Librandi, <a href="/A198694/b198694.txt">Table of n, a(n) for n = 0..1000</a>
%H A198694 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (5,-4).
%F A198694 a(n) = 4*a(n-1)+3.
%F A198694 a(n) = 5*a(n-1)-4*a(n-2), n>1.
%F A198694 G.f.: ( 6-3*x ) / ( (4*x-1)*(x-1) ). - _R. J. Mathar_, Oct 30 2011
%F A198694 E.g.f.: exp(x)*(7*exp(3*x) - 1). - _Stefano Spezia_, Apr 17 2024
%t A198694 7*4^Range[0,30]-1 (* or *) LinearRecurrence[{5,-4},{6,27},30] (* _Harvey P. Dale_, Nov 14 2018 *)
%o A198694 (Magma) [7*4^n-1: n in [0..30]]
%Y A198694 Cf. A024036, A097743, A114569, A156760.
%K A198694 nonn,easy
%O A198694 0,1
%A A198694 _Vincenzo Librandi_, Oct 29 2011