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 A013812 #19 Jul 16 2025 00:57:38 %S A013812 20,3200000,512000000000,81920000000000000,13107200000000000000000, %T A013812 2097152000000000000000000000,335544320000000000000000000000000, %U A013812 53687091200000000000000000000000000000,8589934592000000000000000000000000000000000,1374389534720000000000000000000000000000000000000 %N A013812 a(n) = 20^(4*n + 1). %H A013812 Vincenzo Librandi, <a href="/A013812/b013812.txt">Table of n, a(n) for n = 0..100</a> %H A013812 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>. %H A013812 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (160000). %F A013812 a(n) = 160000*a(n-1). - _Harvey P. Dale_, Dec 30 2012 %F A013812 From _Elmo R. Oliveira_, Jul 13 2025: (Start) %F A013812 G.f.: 20/(1-160000*x). %F A013812 E.g.f.: 20*exp(160000*x). %F A013812 a(n) = A013776(n)*A013792(n) = A009964(A016813(n)). (End) %p A013812 A013812:=n->20^(4*n+1): seq(A013812(n), n=0..10); # _Wesley Ivan Hurt_, Mar 31 2017 %t A013812 20^(4*Range[0,10]+1) (* or *) NestList[160000#&,20,10] (* _Harvey P. Dale_, Dec 30 2012 *) %o A013812 (Magma) [20^(4*n+1): n in [0..15]]; // _Vincenzo Librandi_, Jul 06 2011 %Y A013812 Subsequence of A009964. %Y A013812 Cf. A013776, A013792, A016813. %K A013812 nonn,easy %O A013812 0,1 %A A013812 _N. J. A. Sloane_