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Search: id:A078485
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| A078485 |
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Number of irreducible indecomposable permutations of degree n. |
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+0
2
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| 0, 1, 1, 1, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215, 33554431, 67108863, 134217727, 268435455, 536870911, 1073741823, 2147483647, 4294967295, 8589934591
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OFFSET
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0,5
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REFERENCES
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M. D. Atkinson and T. Stitt, Restricted permutations and the wreath product, Discrete Math., 259 (2002), 19-36.
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FORMULA
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2^(n-1)-1 for n>3. G.f.: x-2*x^3+x/(1-2*x)-x/(1-x).
(1, 7, 15, 31, 63,...) = row sums of triangle A134065. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Oct 06 2007
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CROSSREFS
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Cf. A134065.
Sequence in context: A117747 A137196 A120094 this_sequence A014001 A063592 A146837
Adjacent sequences: A078482 A078483 A078484 this_sequence A078486 A078487 A078488
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KEYWORD
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nonn
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AUTHOR
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njas, Jan 04 2003
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