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 A013899 #19 Sep 26 2023 16:31:07 %S A013899 441,1801088541,7355827511386641,30041942495081691894741, %T A013899 122694327386105632949003612841,501096025171921401632658604207540941, %U A013899 2046526777500669368329342638102622164679041,8358222058517261267863236597617557285387836027141 %N A013899 a(n) = 21^(5*n + 2). %H A013899 Vincenzo Librandi, <a href="/A013899/b013899.txt">Table of n, a(n) for n = 0..50</a> %H A013899 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A013899 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (4084101). %F A013899 a(n) = 4084101*a(n-1), a(0)=441. - _Vincenzo Librandi_, May 27 2011 %t A013899 NestList[4084101#&,441,10] (* _Harvey P. Dale_, Sep 26 2023 *) %o A013899 (Magma) [21^(5*n+2): n in [0..10]]; // _Vincenzo Librandi_, May 27 2011 %Y A013899 Cf. A009965. %K A013899 nonn %O A013899 0,1 %A A013899 _N. J. A. Sloane_