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A119600
a(n) = 4*Product_{i=1..n-1} (3^i+1)^2.
1
4, 4, 64, 6400, 5017600, 33738342400, 2008645953126400, 1070407428421058560000, 5124408580006984170864640000, 220656234047362257307900743516160000, 85495432669493277396354169745064287272960000, 298114237913837782686540845369489025952802406400000000, 9355246290649672947599943358541996936410690283965618585600000000
OFFSET
0,1
LINKS
R. Chapman et al., 2-modular lattices from ternary codes, J. Th. des Nombres de Bordeaux, 14 (2002), 73-85.
FORMULA
a(n) = 4*A290000(n)^2. - Vaclav Kotesovec, Sep 17 2024
MATHEMATICA
Table[4*Product[(3^i+1)^2, {i, n-1}], {n, 0, 12}] (* James C. McMahon, Sep 17 2024 *)
PROG
(PARI) a(n) = 4*prod(i=1, n-1, (3^i+1)^2); \\ Michel Marcus, Oct 28 2015
CROSSREFS
Sequence in context: A214615 A206489 A124399 * A244027 A219796 A222426
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 04 2006
STATUS
approved