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Search: id:A127221
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| 2, 12, 56, 240, 992, 3648, 14464, 57088, 224768, 883712, 3471360, 13651968, 53682176, 211075072, 829915136, 3263102976, 12830244864, 50447253504, 198353354752, 779904614400
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OFFSET
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1,1
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FORMULA
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a(n) = Trace of matrix [({{2,2,2,2,0},{2,0,0,0,0},{0,2,0,0,0),{0,0,2,0,0},{0,0,0,2,0})^n] a(n) = 2^n Trace of matrix [({{1,1,1,1,1},{1,0,0,0,0},{0,1,0,0,0},{0,0,1,0,0},{0,0,0,1,0)^n]
G.f.: -2*x*(1+4*x+12*x^2+32*x^3+80*x^4)/(-1+2*x+4*x^2+8*x^3+16*x^4+32*x^5) [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 11 2009]
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MATHEMATICA
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Table[Tr[MatrixPower[2*{{1, 1, 1, 1, 1}, {1, 0, 0, 0, 0}, {0, 1, 0, 0, 0}, {0, 0, 1, 0, 0}, {0, 0, 0, 1, 0}}, x]], {x, 1, 20}]
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CROSSREFS
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Cf. A087131, A127210, A127211, A127212, A127213, A127214, A127216, A001648, A127220, A127222.
Cf. A023424, A074048.
Sequence in context: A122229 A127216 A006659 this_sequence A020522 A037130 A078543
Adjacent sequences: A127218 A127219 A127220 this_sequence A127222 A127223 A127224
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Jan 09 2007
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EXTENSIONS
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G.f. proposed by Maksym Voznyy checked and corrected by R. J. Mathar, Sep 16 2009.
Definition corrected by R. J. Mathar, Sep 17 2009
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