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Search: id:A008724
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| A008724 |
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a(n) = floor(n^2/12); g.f.: x^4/((1-x)^2*(1-x^6)). |
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+0
4
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| 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 21, 24, 27, 30, 33, 36, 40, 44, 48, 52, 56, 60, 65, 70, 75, 80, 85, 90, 96, 102, 108, 114, 120, 126, 133, 140, 147, 154, 161, 168, 176, 184, 192, 200, 208, 216, 225, 234, 243, 252, 261, 270, 280, 290, 300, 310, 320, 330, 341, 352
(list; graph; listen)
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OFFSET
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0,6
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COMMENT
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With a different offset, Molien series for 3-dimensional group [2,n] = *22n.
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REFERENCES
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P. T. Ho, The crossing number of K_{4,n} on the real projective plane, Discr. Math., 304 (2005). 23-33.
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LINKS
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Index entries for sequences related to linear recurrences with constant coefficients
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 189
Index entries for Molien series
Eric Weisstein's World of Mathematics, ToroidalCrossingNumber
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FORMULA
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a(n)=a(n-6)+n+1 (if 1, 2, 3, ... has offset 0). - Paul Barry (pbarry(AT)wit.ie), Jul 14 2004
a(n) = sum(floor(j/6), {j,0,n+2}), a(n-2) = (1/2)floor(n/6)*(2n-4-6*floor(n/6)) [From Mitch Harris (maharri(AT)gmail.com), Sep 08 2008]
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MAPLE
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x^4/((1-x)^2*(1-x^6));
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CROSSREFS
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Cf. A001399.
Sequence in context: A004279 A120370 A011866 this_sequence A112402 A056864 A029032
Adjacent sequences: A008721 A008722 A008723 this_sequence A008725 A008726 A008727
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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