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A282082
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Number of n-element subsets of [n+6] having an even sum.
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2
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1, 3, 12, 44, 110, 226, 452, 868, 1519, 2485, 3976, 6216, 9324, 13524, 19320, 27192, 37389, 50391, 67188, 88660, 115258, 147862, 188188, 237692, 297115, 367913, 452816, 554064, 672792, 811240, 973488, 1162800, 1380825, 1630827, 1918620, 2248764, 2623558
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: -(x^8-4*x^7+16*x^6-28*x^5+38*x^4-28*x^3+16*x^2-4*x+1) / ((x^2+1)^4*(x-1)^7).
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EXAMPLE
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a(0) = 1: {}.
a(1) = 3: {2}, {4}, {6}.
a(2) = 12: {1,3}, {1,5}, {1,7}, {2,4}, {2,6}, {2,8}, {3,5}, {3,7}, {4,6}, {4,8}, {5,7}, {6,8}.
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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