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%I #20 Sep 08 2022 08:44:38
%S 21,4084101,794280046581,154472377739119461,30041942495081691894741,
%T 5842587018385982521381124421,1136272165922724266740722458520501,
%U 220983347100817338120002444455525554981,42977062327514056734916195400155065458259861
%N a(n) = 21^(4*n + 1).
%H Vincenzo Librandi, <a href="/A013814/b013814.txt">Table of n, a(n) for n = 0..100</a>
%H Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (194481).
%o (Magma) [21^(4*n+1): n in [0..15]]; // _Vincenzo Librandi_, Jul 07 2011
%o (Maxima) makelist(21^(4*n+1),n,0,20); /* _Martin Ettl_, Oct 21 2012 */
%o (PARI) a(n) = 21^(4*n+1); \\ _Altug Alkan_, Sep 08 2018
%K nonn,easy
%O 0,1
%A _N. J. A. Sloane_
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