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A220895
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Number of closed lambda-terms of size n with at most 1 free de Bruijn index.
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3
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1, 3, 13, 76, 542, 4493, 42131, 439031, 5020105, 62382279, 835980065, 12004984120, 183754242626, 2984264710781, 51220227153987, 925859588215096, 17571969962025822, 349210371834021295, 7249185099929421649, 156847124089924073770, 3530125495029323284404
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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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Grygiel and Lescanne give a recurrence.
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MATHEMATICA
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T[0, m_] := m; T[n_, m_] := T[n, m] = T[n-1, m+1] + Sum[T[i, m] T[n-i-1, m], {i, 0, n-1}];
a[n_] := T[n, 1];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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