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%I #11 Jun 29 2023 10:42:47
%S 1,9,189,3969,83349,1750329,36756909,771895089,16209796869,
%T 340405734249,7148520419229,150118928803809,3152497504879989,
%U 66202447602479769,1390251399652075149,29195279392693578129
%N Seventh column of triangle A067417.
%H Vincenzo Librandi, <a href="/A067422/b067422.txt">Table of n, a(n) for n = 0..700</a>
%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (21).
%F a(n) = A067417(n+6, 6).
%F a(n) = 9*(3*7)^(n-1), n >= 1, a(0)=1.
%F G.f.: (1-12*x)/(1-21*x).
%o (Magma) [Ceiling(9*(3*7)^(n-1)): n in [0..20]]; // _Vincenzo Librandi_, Oct 02 2011
%Y Cf. A067421 (sixth column), A067423 (eighth column), A009965 (powers of 21).
%K nonn,easy
%O 0,2
%A _Wolfdieter Lang_, Jan 25 2002
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