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A071009
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Number of solutions (x,y,z,u,v,w) to x+y+z = u+v+w, 0<=x,y,z,u,v,w<=n-1, x>=y>=z, u>=v>=w.
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0
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1, 4, 16, 48, 119, 256, 500, 900, 1525, 2456, 3796, 5664, 8207, 11588, 16004, 21672, 28845, 37800, 48856, 62356, 78691, 98280, 121592, 149128, 181445, 219132, 262840, 313256, 371131, 437256, 512492, 597740, 693977, 802224, 923580
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OFFSET
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1,2
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LINKS
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FORMULA
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Recurrence: a(n) = 3*a(n-1)-a(n-2)-4*a(n-3)+2*a(n-4)+2*a(n-5)+2*a(n-6)-4*a(n-7)-a(n-8)+3*a(n-9)-a(n-10). G.f.: x*(1+x+5*x^2+8*x^3+5*x^4+x^5+x^6)/(1+x+x^2)/(1+x)^2/(1-x)^6.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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