A119600 a(n) = 4*Product_{i=1..n-1} (3^i+1)^2.

4, 4, 64, 6400, 5017600, 33738342400, 2008645953126400, 1070407428421058560000, 5124408580006984170864640000, 220656234047362257307900743516160000, 85495432669493277396354169745064287272960000, 298114237913837782686540845369489025952802406400000000, 9355246290649672947599943358541996936410690283965618585600000000

Offset: 0

Author

N. J. A. Sloane, Jun 04 2006

Keywords

• nonn

Links

• R. Chapman et al., 2-modular lattices from ternary codes, J. Th. des Nombres de Bordeaux, 14 (2002), 73-85.

Crossrefs

Cf. A028362, A290000.

Programs

Mathematica

Table[4*Product[(3^i+1)^2,{i,n-1}],{n,0,12}] (* James C. McMahon, Sep 17 2024 *)

PARI

a(n) = 4*prod(i=1, n-1, (3^i+1)^2); \\ Michel Marcus, Oct 28 2015

Formula

a(n) = 4*A290000(n)^2. - Vaclav Kotesovec, Sep 17 2024