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Search: id:A138749
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| A138749 |
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a(n) = 2*a(n-1) - 5*a(n-2). |
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+0
1
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| -1, -7, -9, 17, 79, 73, -249, -863, -481, 3353, 9111, 1457, -42641, -92567, 28071, 518977, 897599, -799687, -6087369, -8176303, 14084239, 69049993, 67678791, -209892383, -758178721, -466895527, 2857102551, 8048682737, 1811852719, -36619708247
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OFFSET
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1,2
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FORMULA
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a(n) = 2*a(n-1) - 5*a(n-2), n>3. a(n) = left term in [1,-2; 2,1]^n * [1,1].
O.g.f.: -x*(1+5*x)/(1-2*x+5*x^2). a(n)=-A045873(n)-5*A045873(n-1). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 03 2008
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EXAMPLE
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a(5) = 79 = 2*a(4) - 5*a(3) = 2*17 - 5*(-9).
a(5) = 79 = left term in [1,-2, 2,1]^5.
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CROSSREFS
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Sequence in context: A140364 A022321 A116484 this_sequence A053803 A032791 A046257
Adjacent sequences: A138746 A138747 A138748 this_sequence A138750 A138751 A138752
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KEYWORD
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sign
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 28 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 03 2008
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