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 A248226 #23 Mar 09 2025 12:24:25
%S A248226 0,7,91,973,9919,99757,999271,9997813,99993439,999980317,9999940951,
%T A248226 99999822853,999999468559,9999998405677,99999995217031,
%U A248226 999999985651093,9999999956953279,99999999870859837,999999999612579511,9999999998837738533,99999999996513215599
%N A248226 a(n) = 10^n - 3^n.
%H A248226 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (13,-30).
%F A248226 G.f.: 7*x/((1 - 3*x)*(1 - 10*x)).
%F A248226 a(n) = 13*a(n-1) - 30*a(n-2).
%F A248226 a(n) = A011557(n) - A000244(n).
%F A248226 a(2*n) mod 10^n = A016189(n). - _Michel Marcus_, Oct 05 2014
%F A248226 a(n+1) = 7*A016145(n). - _Bruno Berselli_, Oct 05 2014
%F A248226 E.g.f.: exp(3*x)*(exp(7*x) - 1). - _Stefano Spezia_, Mar 09 2025
%t A248226 Table[10^n - 3^n, {n, 0, 25}] (* or *) CoefficientList[Series[(7 x)/((1 - 3 x) (1 - 10 x)), {x, 0, 30}], x]
%t A248226 LinearRecurrence[{13,-30},{0,7},30] (* _Harvey P. Dale_, Jul 10 2021 *)
%o A248226 (Magma) [10^n-3^n: n in [0..30]];
%o A248226 (PARI) a(n) = 10^n - 3^n \\ _Michel Marcus_, Oct 05 2014
%Y A248226 Cf. similar sequences listed in A248225.
%Y A248226 Cf. A016145, A016189.
%K A248226 nonn,easy
%O A248226 0,2
%A A248226 _Vincenzo Librandi_, Oct 05 2014