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Search: id:A008579
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| A008579 |
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Coordination sequence for planar net 3.6.3.6. Spherical growth function for certain reflection group in plane. |
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+0
2
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| 1, 4, 8, 14, 18, 22, 28, 30, 38, 38, 48, 46, 58, 54, 68, 62, 78, 70, 88, 78, 98, 86, 108, 94, 118, 102, 128, 110, 138, 118, 148, 126, 158, 134, 168, 142, 178, 150, 188, 158, 198, 166, 208, 174, 218, 182
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Interesting because coefficients never become monotonic.
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REFERENCES
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P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 161 (but beware errors).
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
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FORMULA
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G.f.: (1+2*x)*(1+2*x+2*x^2+2*x^3-x^4)/(1-x^2)^2.
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MAPLE
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f := n->if n mod 2 = 0 then 10*(n/2)-2 else 8*(n-1)/2+6 fi;
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CROSSREFS
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Sequence in context: A114971 A036312 A024805 this_sequence A022804 A067699 A066941
Adjacent sequences: A008576 A008577 A008578 this_sequence A008580 A008581 A008582
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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