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Search: id:A007752
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| 1, 24, 391, 6240, 99457, 1585080, 25261831, 402604224, 6416405761, 102259887960, 1629741801607, 25973608937760, 413948001202561, 6597194410303224, 105141162563649031, 1675661406608081280
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Mentioned in a problem on p. 334 of Two-Year College Math. Jnl., Vol. 25, 1994.
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FORMULA
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G.f.: x(1+7x)/((1-x)(1-16x+x^2)). a(n)=16a(n-1)-a(n-2)+8.
a(n)=-4/7+(11/14)*[8-3*sqrt(7)]^n+(11/14)*[8+3*sqrt(7)]^n+(2/7)*sqrt(7)*[8+3*sqrt(7)]^n-(2/7) *[8-3*sqrt(7)]^n*sqrt(7), with n>=0 - Paolo P. Lava (ppl(AT)spl.at), Jun 19 2008
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PROGRAM
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(PARI) a(n)=local(w); w=8+3*quadgen(28); imag(1/w^n)+4*(real(1/w^n)-1)/7
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CROSSREFS
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Cf. A007750, A007751.
Adjacent sequences: A007749 A007750 A007751 this_sequence A007753 A007754 A007755
Sequence in context: A020573 A022448 A025947 this_sequence A145602 A020447 A021894
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KEYWORD
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nonn
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AUTHOR
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John C. Hallyburton, Jr. [ hallyb(AT)vmsdev.enet.dec.com ].
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EXTENSIONS
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Edited by Michael Somos, Jul 27, 2002
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