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 A013766 #27 Mar 01 2025 23:23:35 %S A013766 20,160000,1280000000,10240000000000,81920000000000000, %T A013766 655360000000000000000,5242880000000000000000000, %U A013766 41943040000000000000000000000,335544320000000000000000000000000,2684354560000000000000000000000000000,21474836480000000000000000000000000000000 %N A013766 a(n) = 20^(3*n + 1). %H A013766 Vincenzo Librandi, <a href="/A013766/b013766.txt">Table of n, a(n) for n = 0..200</a> %H A013766 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>. %H A013766 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (8000). %F A013766 From _Elmo R. Oliveira_, Feb 27 2025: (Start) %F A013766 G.f.: 20/(1 - 8000*x). %F A013766 E.g.f.: 20*exp(8000*x). %F A013766 a(n) = A013730(n)*A013746(n) = A009964(A016777(n)). (End) %t A013766 20^(3Range[0,10]+1) (* _Harvey P. Dale_, Jun 23 2011 *) %o A013766 (Magma) [20^(3*n+1): n in [0..10]]; // _Vincenzo Librandi_, Jun 27 2011 %o A013766 (Maxima) makelist(20^(3*n+1),n,0,20); /* _Martin Ettl_, Oct 21 2012 */ %o A013766 (PARI) a(n)=20^(3*n+1) \\ _Charles R Greathouse IV_, Jul 10 2016 %Y A013766 Subsequence of A009964. %Y A013766 Cf. A013730, A013746, A016777. %K A013766 nonn,easy %O A013766 0,1 %A A013766 _N. J. A. Sloane_