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%I #14 Jun 30 2023 14:26:21
%S 4,1,24,6,144,36,864,216,5184,1296,31104,7776,186624,46656,1119744,
%T 279936,6718464,1679616,40310784,10077696,241864704,60466176,
%U 1451188224,362797056,8707129344,2176782336,52242776064,13060694016,313456656384
%N a(n) = 6*a(n-2) for n > 2; a(1) = 4, a(2) = 1.
%C Interleaving of 4*A000400 and A000400.
%H Vincenzo Librandi, <a href="/A166027/b166027.txt">Table of n, a(n) for n = 1..300</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0, 6).
%F a(n) = 6^(1/4*(2*n+3+(-1)^n))*(25-23*(-1)^n)/72.
%F G.f.: x*(4+x)/(1-6*x^2).
%t Join[{4, 1, 24}, LinearRecurrence[{0, 6}, {6, 144}, 25]] (* _G. C. Greubel_, Apr 21 2016 *)
%o (Magma) [ n le 2 select 7-3*n else 6*Self(n-2): n in [1..29] ];
%Y Cf. A000400 (powers of 6), A166023.
%K nonn,easy
%O 1,1
%A _Klaus Brockhaus_, Oct 04 2009