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a(n) = 20^(4*n+1).
1

%I #16 Sep 08 2022 08:44:38

%S 20,3200000,512000000000,81920000000000000,13107200000000000000000,

%T 2097152000000000000000000000,335544320000000000000000000000000,

%U 53687091200000000000000000000000000000,8589934592000000000000000000000000000000000

%N a(n) = 20^(4*n+1).

%H Vincenzo Librandi, <a href="/A013812/b013812.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 (160000).

%F a(n) = 160000*a(n-1). - _Harvey P. Dale_, Dec 30 2012

%p A013812:=n->20^(4*n+1): seq(A013812(n), n=0..10); # _Wesley Ivan Hurt_, Mar 31 2017

%t 20^(4*Range[0,10]+1) (* or *) NestList[160000#&,20,10] (* _Harvey P. Dale_, Dec 30 2012 *)

%o (Magma) [20^(4*n+1): n in [0..15]]; // _Vincenzo Librandi_, Jul 06 2011

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_