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A008724
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floor(n^2/12).
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11
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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; refs; listen; history; internal format)
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OFFSET
| 0,6
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COMMENTS
| With a different offset, Molien series for 3-dimensional group [2,n] = *22n.
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REFERENCES
| 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
| Vincenzo Librandi, Table of n, a(n) for n = 0..10000
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 189
Index entries for Molien series
Eric Weisstein's World of Mathematics, ToroidalCrossingNumber
Index to sequences with linear recurrences with constant coefficients, signature (2,-1,0,0,0,1,-2,1).
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FORMULA
| 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]
G.f.: x^4/((1-x)^2*(1-x^6)).
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MAPLE
| x^4/((1-x)^2*(1-x^6));
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MATHEMATICA
| s=0; lst={}; Do[AppendTo[lst, s+=n]; AppendTo[lst, s+=n]; AppendTo[lst, s+=n]; AppendTo[lst, s+=n]; AppendTo[lst, s+=n]; AppendTo[lst, s+=n], {n, 0, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 14 2010]
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PROG
| (MAGMA) a008724:=func< n | Floor(n^2/12) >; [ a008724(n): n in [0..70] ];
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CROSSREFS
| Cf. A001399.
Sequence in context: A120370 A011866 A174709 * A112402 A056864 A029032
Adjacent sequences: A008721 A008722 A008723 * A008725 A008726 A008727
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Minor edits by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Nov 24 2010
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