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A152299 A threes sequence that gets more even factors out: a(n)=(3^n - 1)*(3^n + 1)/2^(4 - Mod[n, 2]). 0
1, 5, 91, 410, 7381, 33215, 597871, 2690420, 48427561, 217924025, 3922632451, 17651846030, 317733228541, 1429799528435, 25736391511831, 115813761803240, 2084647712458321, 9380914706062445, 168856464709124011 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..18.

FORMULA

a(n)=(3^n - 1)*(3^n + 1)/2^(4 - Mod[n, 2]).

a(n)=82*a(n-2)-81*a(n-4). G.f.: (1+5x+9x^2)/((1-x)(1-9x)(1+x)(1+9x)). [From R. J. Mathar, Dec 04 2008]

MATHEMATICA

Clear[a, n];

a[n_] :=(3^n - 1)*(3^n + 1)/2^(4 - Mod[n, 2]);

Table[a[n], {n, 0, 30}]

CROSSREFS

A003462, A002452

Sequence in context: A158073 A038636 A282052 * A355371 A242945 A243198

Adjacent sequences: A152296 A152297 A152298 * A152300 A152301 A152302

KEYWORD

nonn

AUTHOR

Roger L. Bagula, Dec 02 2008

STATUS

approved

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Last modified December 8 07:38 EST 2022. Contains 358691 sequences. (Running on oeis4.)