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 A196662 #24 Mar 18 2025 15:11:29
%S A196662 1,7,70,700,7000,70000,700000,7000000,70000000,700000000,7000000000,
%T A196662 70000000000,700000000000,7000000000000,70000000000000,
%U A196662 700000000000000,7000000000000000,70000000000000000,700000000000000000,7000000000000000000,70000000000000000000
%N A196662 Expansion of g.f. (1-3*x)/(1-10*x).
%H A196662 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (10).
%F A196662 a(0) = 1, a(n) = 7*10^(n-1) for n>0.
%F A196662 a(n) = Sum_{k=0..n} A193722(n,k)*3^k.
%F A196662 From _Elmo R. Oliveira_, Mar 18 2025: (Start)
%F A196662 E.g.f.: (7*exp(10*x) + 3)/10.
%F A196662 a(n) = 10*a(n-1). (End)
%t A196662 CoefficientList[Series[(1-3x)/(1-10x),{x,0,20}],x] (* or *) LinearRecurrence[ {10},{1,7},30] (* or *) Join[{1},NestList[10#&,7,20]] (* _Harvey P. Dale_, Dec 18 2021 *)
%Y A196662 Cf. A002001, A193722, A196661.
%K A196662 nonn,easy
%O A196662 0,2
%A A196662 _Philippe Deléham_, Oct 05 2011