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Search: id:A084069
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| A084069 |
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Numbers n such that 7*n^2=floor(n*sqrt(7)*ceil(n*sqrt(7))). |
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+0
4
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| 1, 3, 17, 48, 271, 765, 4319, 12192, 68833, 194307, 1097009, 3096720, 17483311, 49353213, 278635967, 786554688, 4440692161, 12535521795, 70772438609, 199781794032, 1127918325583, 3183973182717, 17975920770719, 50743789129440
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OFFSET
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1,2
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FORMULA
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a(1)=1, a(2)=3, a(2n)=6*a(2n-1)-a(2n-2); a(2n+1)=3*a(2n)-a(2n-1)
a(n)a(n+3) = -3 + a(n+1)a(n+2).
G.f.: (1+3x+x^2)/(1-16x+x^2).
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CROSSREFS
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Cf. A001653, A001353, A060645, A001078, A001109, A084068, A084070.
Cf. A001080.
Sequence in context: A095697 A154304 A144640 this_sequence A132124 A011917 A018691
Adjacent sequences: A084066 A084067 A084068 this_sequence A084070 A084071 A084072
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), May 10 2003
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