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Search: id:A008804
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| A008804 |
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Expansion of 1/((1-x)^2*(1-x^2)*(1-x^4)). |
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+0
8
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| 1, 2, 4, 6, 10, 14, 20, 26, 35, 44, 56, 68, 84, 100, 120, 140, 165, 190, 220, 250, 286, 322, 364, 406, 455, 504, 560, 616, 680, 744, 816, 888, 969, 1050, 1140, 1230, 1330, 1430, 1540, 1650, 1771, 1892, 2024
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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b(n)=a(n-3) is the number of asymmetric nonnegative integer 2 X 2 matrices with sum of elements equal to n, under action of dihedral group D_4(b(0)=b(1)=b(2)=0). G.f. for b(n) is x^3/((1-x)^2*(1-x^2)*(1-x^4)) - Vladeta Jovovic (vladeta(AT)Eunet.yu), May 07 2000
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 197
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FORMULA
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For a formula for a(n) see A014557.
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EXAMPLE
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There are 10 asymmetric nonnegative integer 2 X 2 matrices with sum of elements equal to 7 under action of D_4:
[0 0] [0 0] [0 0] [0 1] [0 1] [0 1] [0 1] [0 2] [0 2] [1 1]
[1 6] [2 5] [3 4] [2 4] [3 3] [4 2] [5 1] [3 2] [4 1] [2 3].
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MAPLE
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1/((1-x)^2*(1-x^2)*(1-x^4));
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CROSSREFS
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Cf. A014557, A005232, A053307.
Sequence in context: A094589 A071425 A115065 this_sequence A001307 A088932 A088954
Adjacent sequences: A008801 A008802 A008803 this_sequence A008805 A008806 A008807
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KEYWORD
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nonn,nice,easy
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AUTHOR
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njas
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