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A211475
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Signed partitions of n into n parts in {-n..n} (allowing zero as a part).
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1
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1, 2, 7, 27, 121, 587, 2983, 15744, 85375, 473259, 2670383, 15293119, 88686530, 519864702, 3075894246, 18348407371, 110244289384, 666651567920, 4054481396896, 24786629709850, 152241407914480, 939069024577371, 5815027475345028, 36137289604644570
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OFFSET
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1,2
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COMMENTS
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The normal definition of signed partitions does not allow zero as a part.
Signed partitions of n into n parts in {-n..n}\{0}: A211474.
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LINKS
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EXAMPLE
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a(3) = 7: (-3,3,3), (-2,2,3), (-1,1,3), (-1,2,2), (0,0,3), (0,1,2), (1,1,1).
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MAPLE
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b:= proc(h, i, t, n) option remember;
`if`(i=0, `if`(h=0, 1, 0), `if`(h<0 or i*n<h, 0,
add (b(h+j, i-1, j, n), j=-n..t)))
end:
a:= n-> b(n$4):
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MATHEMATICA
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Table[(IntegerPartitions[n, {1, n}] // Length) + Sum[Sum[(IntegerPartitions[k, {j}, Range[n]] // Length) * (IntegerPartitions[n + k, {1, n - j}, Range[n]] // Length), {j, 0, n - 2}], {k, 1, n*Floor[(n - 1)/2]}], {n, 14}]
(* Second program: *)
b[h_, i_, t_, n_] := b[h, i, t, n] =
If[i == 0, If[h == 0, 1, 0], If[h < 0 || i*n < h, 0,
Sum[b[h + j, i - 1, j, n], {j, Range[-n, t]}]]];
a[n_] := b[n, n, n, n];
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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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