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A000560
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Number of ways of folding a strip of n labeled stamps.
(Formerly M1420 N0557)
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9
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1, 2, 5, 12, 33, 87, 252, 703, 2105, 6099, 18689, 55639, 173423, 526937, 1664094, 5137233, 16393315, 51255709, 164951529, 521138861, 1688959630, 5382512216, 17547919924, 56335234064, 184596351277, 596362337295, 1962723402375
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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2,2
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REFERENCES
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A. Sade, Sur les Chevauchements des Permutations, published by the author, Marseille, 1949.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. B. Wells, Elements of Combinatorial Computing. Pergamon, Oxford, 1971, p. 238.
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LINKS
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R. Dickau, Stamp Folding [Cached copy, pdf format, with permission]
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FORMULA
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a(n) = (1/2)*A000682(n+1) for n >= 2.
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MATHEMATICA
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A000682 = Import["https://oeis.org/A000682/b000682.txt", "Table"][[All, 2]];
A000136 = Import["https://oeis.org/A000136/b000136.txt", "Table"][[All, 2]];
a[n_] := A000136[[n + 1]]/(2 n + 2);
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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EXTENSIONS
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Computed to n = 45 by Iwan Jensen - see link in A000682.
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STATUS
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approved
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