%I #21 Sep 08 2022 08:44:38

%S 21,194481,1801088541,16679880978201,154472377739119461,

%T 1430568690241985328321,13248496640331026125580781,

%U 122694327386105632949003612841,1136272165922724266740722458520501,10523016528610349434285830688358359761

%N a(n) = 21^(3*n + 1).

%H Vincenzo Librandi, <a href="/A013768/b013768.txt">Table of n, a(n) for n = 0..200</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 (9261).

%t 21^(3*Range[0,10]+1) (* or *) NestList[9261#&,21,10] (* _Harvey P. Dale_, Apr 30 2020 *)

%o (Magma) [21^(3*n+1): n in [0..10]]; // _Vincenzo Librandi_, Jun 27 2011

%o (PARI) a(n)=21^(3*n+1) \\ _Charles R Greathouse IV_, Jul 10 2016

%Y Subsequence of A009965.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_