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A003674
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2^(n-1)*( 2^n - (-1)^n ).
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1
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0, 3, 6, 36, 120, 528, 2016, 8256, 32640, 131328, 523776, 2098176, 8386560, 33558528, 134209536, 536887296, 2147450880, 8590000128, 34359607296, 137439215616, 549755289600, 2199024304128, 8796090925056
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OFFSET
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0,2
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COMMENTS
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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]
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REFERENCES
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M. Gardner, Riddles of the Sphinx, New Mathematical Library, M.A.A., 1987, p. 145. Math. Rev. 89i:00015.
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LINKS
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Table of n, a(n) for n=0..22.
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FORMULA
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G.f.: 3x/((1+2x)(1-4x)).
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PROG
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(PARI) a(n)=if(n<0, 0, 2^(n-1)*(2^n-(-1)^n))
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CROSSREFS
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Sequence in context: A084260 A076983 A068084 * A211895 A240986 A120595
Adjacent sequences: A003671 A003672 A003673 * A003675 A003676 A003677
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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