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a(n) = ((3^n - 1)*(3^n + 1))^2/2^(7 - (n mod 2)).
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%I #13 Jan 15 2025 19:38:10

%S 0,1,50,8281,336200,54479161,2206472450,357449732641,14476719552800,

%T 2345228664408721,94981761344401250,15387045345638267401,

%U 623175336533653521800,100954404519087336988681,4088653383025896747098450,662361848050246745812972561

%N a(n) = ((3^n - 1)*(3^n + 1))^2/2^(7 - (n mod 2)).

%H G. C. Greubel, <a href="/A152258/b152258.txt">Table of n, a(n) for n = 0..500</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,6643,0,-538083,0,531441).

%F a(n) = ((3^n - 1)*(3^n + 1))^2 / 2^(7 - (n mod 2)).

%F a(n) = 6643*a(n-2) - 538083*a(n-4) + 531441*a(n-6). - _R. J. Mathar_, Dec 04 2008

%t Table[(9^n-1)^2/2^(7-Mod[n,2]), {n,0,30}]

%o (Magma) [2^((n mod 2) -7)*(9^n-1)^2: n in [0..40]]; // _G. C. Greubel_, May 22 2023

%o (SageMath) [(9^n-1)^2//2^(7-(n%2)) for n in range(41)] # _G. C. Greubel_, May 22 2023

%Y Cf. A002452, A003462.

%K nonn

%O 0,3

%A _Roger L. Bagula_, Dec 01 2008