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A196237
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Number of different ways to select 10 disjoint subsets from {1..n} with equal element sum.
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7
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1, 3, 15, 44, 179, 741, 2989, 13932, 79433, 456134, 3096812, 21083037, 151022325, 1119202826, 8627014654
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OFFSET
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19,2
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LINKS
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EXAMPLE
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a(20) = 3: {1,18}, {2,17}, {3,16}, {4,15}, {5,14}, {6,13}, {7,12}, {8,11}, {9,10}, {19} have element sum 19; {1,19}, {2,18}, {3,17}, {4,16}, {5,15}, {6,14}, {7,13}, {8,12}, {9,11}, {20} have element sum 20; {1,20}, {2,19}, {3,18}, {4,17}, {5,16}, {6,15}, {7,14}, {8,13}, {9,12}, {10,11} have element sum 21.
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MATHEMATICA
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b[l_, n_, k_] := b[l, n, k] = Module[{i, j}, If[l == Array[0 &, k], 1, If[Total[l] > n*(n - 1)/2, 0, b[l, n - 1, k]] + Sum[If[l[[j]] - n < 0, 0, b[Sort[Table[l[[i]] - If[i == j, n, 0], {i, 1, k}]], n - 1, k]], {j, 1, k}]]];
T[n_, k_] := Sum[b[Array[t &, k], n, k], {t, 2*k - 1, Floor[n*(n + 1)/(2*k) ]}]/k!;
a[n_] := T[n, 10];
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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