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%I #13 Sep 08 2022 08:46:04
%S 1,9,243,19683,4782969,3486784401,7625597484987,50031545098999707,
%T 984770902183611232881,58149737003040059690390169,
%U 10301051460877537453973547267843,5474401089420219382077155933569751763,8727963568087712425891397479476727340041449
%N a(n) = 3^((n-1)*(n+2)/2).
%H Vincenzo Librandi, <a href="/A217628/b217628.txt">Table of n, a(n) for n = 1..60</a>
%F a(1) = 1, a(n) = a(n-1) * 3^n.
%F G.f.: G(0)/(2*x^3) - 1/(3*x)- 1/(3*x^2)- 1/(2*x^3), where G(k)= 1 + 3^(k-1)*x/(1 - 1/(1 + 1/G(k+1) )); (continued fraction). - _Sergei N. Gladkovskii_, Jul 28 2013
%t Table[3^((n-1) * (n+2)/2), {n, 1, 30}]
%o (Magma) I:=[1]; [n le 1 select I[n] else Self(n-1)*3^n: n in [1..20]]
%o (Maxima) A217628[n]:=3^((n-1)*(n+2)/2)$
%o makelist(A217628[n],n,1,30); /* _Martin Ettl_, Oct 29 2012 */
%Y Cf. A036442.
%K nonn
%O 1,2
%A _Vincenzo Librandi_, Oct 24 2012
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