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Search: id:A122910
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| A122910 |
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Expansion of (1-2x-3x^2)/((1-2x)(1+4x)(1-8x)). |
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+0
2
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| 1, 4, 45, 302, 2636, 20184, 165040, 1305952, 10504896, 83809664, 671394560, 5367485952, 42954566656, 343577810944, 2748857364480, 21989919383552, 175923113148416, 1407369872769024, 11259019111628800, 90071912374730752
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OFFSET
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0,2
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COMMENT
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Let M be the matrix M(n,k)=J(k+1)*sum{j=0..n, (-1)^(n-j)C(n,j)C(j+1,k+1)}. a(n) gives the row sums of M^3.
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FORMULA
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G.f.: (1-2x-3x^2)/(1-6x-24x^2+64x^3); a(n)=5*8^n/8+7*(-4)^n/24+2^n/12; a(n)=J(n)*A083424(n-1)+J(n+1)*A083424(n) where J(n) are the Jacobsthal numbers A001045(n).
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CROSSREFS
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Sequence in context: A132998 A120075 A123650 this_sequence A117644 A055602 A073565
Adjacent sequences: A122907 A122908 A122909 this_sequence A122911 A122912 A122913
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Sep 18 2006
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