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A218149 a(n) = 3^((6+5*n+n^3)/6). 2
1, 3, 9, 81, 6561, 14348907, 2541865828329, 109418989131512359209, 3433683820292512484657849089281, 235655016338368235499067731945871638181119123, 106111661199647248543687855752712667991103904330482569981872649 (list; graph; refs; listen; history; text; internal format)
OFFSET
-1,2
COMMENTS
a(n) = a(0) * product(i=1,2,...k)r(i)^C(n,i), C(n,i)=0 for all i > n.
Here, it is submitted a special case of the geometric-geometric sequence having finite ratios, that is, k consecutive rows of ratios, whose first terms are r(1), r(2), r(3),..., r(k), the last row (k-th row) being of a constant ratio, with k=3, a(0)=r(1)=r(2)=r(3)=3.
LINKS
FORMULA
a(n) = a(n-1)*(2^(1+n*(n-1)/2)), with a(0)=3
EXAMPLE
a(3) = 3^((6+5*3+3^3)/6) = 3^((6+15+27)/6) = 3^(48/6) = 3^8 = 6561.
PROG
(Maxima) A218149(n):=3^((6+5*n+n^3)/6)$
makelist(A218149(n), n, -1, 10); /* Martin Ettl, Oct 31 2012 */
(PARI) a(n)=3^(n*(5+n^2)/6+1) \\ Charles R Greathouse IV, Jan 06 2013
CROSSREFS
Cf. A006125.
Sequence in context: A032108 A216206 A038062 * A011764 A018624 A274032
KEYWORD
nonn,easy
AUTHOR
Mokhtar Mohamed, Oct 22 2012
STATUS
approved

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Last modified February 20 19:07 EST 2024. Contains 370217 sequences. (Running on oeis4.)