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A003674 2^(n-1)*( 2^n - (-1)^n ). 1
0, 3, 6, 36, 120, 528, 2016, 8256, 32640, 131328, 523776, 2098176, 8386560, 33558528, 134209536, 536887296, 2147450880, 8590000128, 34359607296, 137439215616, 549755289600, 2199024304128, 8796090925056 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Given the 2x2 matrix M = [1,3; 3,1], a(n) = term (1,2) in M^n, n>0. [From Gary W. Adamson, Aug 06 2010]

REFERENCES

M. Gardner, Riddles of the Sphinx, New Mathematical Library, M.A.A., 1987, p. 145. Math. Rev. 89i:00015.

LINKS

Table of n, a(n) for n=0..22.

FORMULA

G.f.: 3x/((1+2x)(1-4x)).

PROG

(PARI) a(n)=if(n<0, 0, 2^(n-1)*(2^n-(-1)^n))

CROSSREFS

Sequence in context: A084260 A076983 A068084 * A211895 A240986 A120595

Adjacent sequences:  A003671 A003672 A003673 * A003675 A003676 A003677

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified February 21 11:25 EST 2019. Contains 320372 sequences. (Running on oeis4.)