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 A013813 #19 Jul 21 2025 08:57:50 %S A013813 8000,1280000000,204800000000000,32768000000000000000, %T A013813 5242880000000000000000000,838860800000000000000000000000, %U A013813 134217728000000000000000000000000000,21474836480000000000000000000000000000000,3435973836800000000000000000000000000000000000 %N A013813 a(n) = 20^(4*n + 3). %H A013813 Vincenzo Librandi, <a href="/A013813/b013813.txt">Table of n, a(n) for n = 0..100</a> %H A013813 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>. %H A013813 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (160000). %F A013813 From _Elmo R. Oliveira_, Jul 13 2025: (Start) %F A013813 G.f.: 8000/(1-160000*x). %F A013813 E.g.f.: 8000*exp(160000*x). %F A013813 a(n) = 160000*a(n-1). %F A013813 a(n) = A013777(n)*A013793(n) = A009964(A004767(n)). (End) %t A013813 20^(4*Range[0, 10] + 3) (* or *) %t A013813 NestList[160000*# &, 8000, 10] (* _Paolo Xausa_, Jul 21 2025 *) %o A013813 (Magma) [20^(4*n+3): n in [0..15]]; // _Vincenzo Librandi_, Jul 06 2011 %Y A013813 Subsequence of A009964. %Y A013813 Cf. A004767, A013777, A013793. %K A013813 nonn,easy %O A013813 0,1 %A A013813 _N. J. A. Sloane_