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%I #18 Sep 18 2024 05:36:48
%S 4,4,64,6400,5017600,33738342400,2008645953126400,
%T 1070407428421058560000,5124408580006984170864640000,
%U 220656234047362257307900743516160000,85495432669493277396354169745064287272960000,298114237913837782686540845369489025952802406400000000,9355246290649672947599943358541996936410690283965618585600000000
%N a(n) = 4*Product_{i=1..n-1} (3^i+1)^2.
%H R. Chapman et al., <a href="http://dx.doi.org/10.5802/jtnb.347">2-modular lattices from ternary codes</a>, J. Th. des Nombres de Bordeaux, 14 (2002), 73-85.
%F a(n) = 4*A290000(n)^2. - _Vaclav Kotesovec_, Sep 17 2024
%t Table[4*Product[(3^i+1)^2,{i,n-1}],{n,0,12}] (* _James C. McMahon_, Sep 17 2024 *)
%o (PARI) a(n) = 4*prod(i=1, n-1, (3^i+1)^2); \\ _Michel Marcus_, Oct 28 2015
%Y Cf. A028362, A290000.
%K nonn
%O 0,1
%A _N. J. A. Sloane_, Jun 04 2006