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Search: id:A014990
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| 1, -7, 57, -455, 3641, -29127, 233017, -1864135, 14913081, -119304647, 954437177, -7635497415, 61083979321, -488671834567, 3909374676537, -31274997412295, 250199979298361, -2001599834386887, 16012798675095097
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n) = a(n-1) + q^{(n-1)} = {(q^n - 1) / (q - 1)}
a(1)=1, a(2)=-7, a(n)=-7*a(n-1)+8*a(n-2) for n>2 . a(n)=(-1)^(n+1)*A015565(n) . G.f.:x/(1+7*x-8*x^2) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Feb 13 2007
a(n)=(1/9)*[1+8*(-8)^n], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Nov 21 2008]
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MAPLE
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a:=n->sum ((-8)^j, j=0..n): seq(a(n), n=0..25); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 16 2008]
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PROGRAM
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(Other) sage: [gaussian_binomial(n, 1, -8) for n in xrange(1, 20)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 28 2009]
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CROSSREFS
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Cf. A015565.
A077925, A014983, A014985, A014986, A014987, A014989, A014991, A014992, A014993, A014994 [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 16 2008]
Sequence in context: A110830 A042187 A082310 this_sequence A015565 A082413 A142990
Adjacent sequences: A014987 A014988 A014989 this_sequence A014991 A014992 A014993
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KEYWORD
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sign,easy
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AUTHOR
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Olivier Gerard (olivier.gerard(AT)gmail.com)
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