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Search: id:A061866
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| A061866 |
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a(n) = DivSumChoose(n,3), the number of solutions to x+y+z = 0 mod 3, where 1 <= x < y < z <= n. |
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+0
3
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| 0, 0, 0, 1, 2, 4, 8, 13, 20, 30, 42, 57, 76, 98, 124, 155, 190, 230, 276, 327, 384, 448, 518, 595, 680, 772, 872, 981, 1098, 1224, 1360, 1505, 1660, 1826, 2002, 2189, 2388, 2598, 2820, 3055, 3302, 3562, 3836, 4123, 4424, 4740, 5070, 5415, 5776, 6152, 6544, 6953, 7378, 7820
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OFFSET
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0,5
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COMMENT
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(1+x)*(1+x^2)*(1+x^3) / ( (1-x)*(1-x^2)*(1-x^3)*(1-x^4)) is the Poincare series (or Molien series) for H^*(O_4(q); F_2).
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REFERENCES
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A. Adem and R. J. Milgram, Cohomology of Finite Groups, Springer-Verlag, 2nd. ed., 2004; p. 233.
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FORMULA
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G.f.: x^3*(1+x)*(1+x^2)*(1+x^3) / ( (1-x)*(1-x^2)*(1-x^3)*(1-x^4)). - N. J. A. Sloane (njas(AT)research.att.com), Mar 17 2004
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CROSSREFS
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The third diagonal of A061865.
Sequence in context: A084684 A011907 A056133 this_sequence A130840 A115266 A026039
Adjacent sequences: A061863 A061864 A061865 this_sequence A061867 A061868 A061869
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KEYWORD
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nonn
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AUTHOR
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Antti Karttunen May 11 2001
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