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Search: id:A138377
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| A138377 |
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a(0) = 0, a(1) = 1, a(2) = 3, a(3) = 2; thereafter a(n)=-4a(n-4). |
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+0
6
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| 0, 1, 3, 2, 0, -4, -12, -8, 0, 16, 48, 32, 0, -64, -192, -128, 0, 256, 768, 512, 0, -1024, -3072, -2048, 0, 4096, 12288, 8192, 0, -16384, -49152, -32768, 0, 65536, 196608, 131072, 0, -262144, -786432, -524288, 0, 1048576, 3145728, 2097152, 0, -4194304, -12582912, -8388608, 0, 16777216, 50331648
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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First and third differences have only 2^n's.
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FORMULA
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O.g.f.: x(1+x)(2x+1)/((1-2x+2x^2)(1+2x+2x^2)). a(n)= (5*A009545(n)-A108520(n))/4. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 09 2008
Ogf([0, 1, 3, 2, 0, -4, -12, -8, 0, 16, 48, 32, 0, -64, -192, -128, 0, 256, 768, 512, 0]) = (2*x^3 + 3*x^2 + x)/(4*x^4 + 1) - Alexander R. Povolotsky (pevnev(AT)juno.com), May 08 2008
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CROSSREFS
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Cf. A138380, A138382.
Sequence in context: A127571 A143612 A011231 this_sequence A021316 A092092 A086800
Adjacent sequences: A138374 A138375 A138376 this_sequence A138378 A138379 A138380
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KEYWORD
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sign,easy
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AUTHOR
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Paul Curtz (bpcrtz(AT)free.fr), May 08 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 09 2008
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