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A270756
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Total sum of the sizes of all blocks with maximal element 2 in all set partitions of {1,2,...,n}.
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3
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3, 4, 9, 25, 82, 307, 1283, 5894, 29427, 158269, 910520, 5570737, 36071631, 246188196, 1764757189, 13246059237, 103825154098, 847806545767, 7196895817375, 63389642645486, 578318132627495, 5456455370760825, 53165437331978992, 534262881004973981
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OFFSET
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2,1
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LINKS
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MATHEMATICA
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b[n_, m_, t_] := b[n, m, t] = If[n == 0, {1, 0}, Sum[If[t == 1 && j != m + 1, 0, Function[p, p + If[j == -t || t == 1 && j == m + 1, {0, p[[1]]}, 0]][b[n - 1, Max[m, j], If[t == 1 && j == m + 1, -j, If[t < 0, t, If[t > 0, t - 1, 0]]]]]], {j, 1, m + 1}]];
a[n_] := b[n, 0, Max[0, 1 + n - 2]][[2]];
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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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