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Search: id:A122031
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| A122031 |
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a(n) = a(n - 1) + (n - 1)*a(n - 2). |
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+0
1
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| 1, 2, 3, 7, 16, 44, 124, 388, 1256, 4360, 15664, 59264, 231568, 942736, 3953120, 17151424, 76448224, 350871008, 1650490816, 7966168960, 39325494464, 198648873664, 1024484257408, 5394759478016, 28957897398400
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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Paul Abbott (paul(AT)physics.uwa.edu.au) gives a generating function: Needs["DiscreteMath`RSolve`"]; ExponentialGeneratingFunction[{a[0] == 1, a[1] == 2, a[n] == a[n - 1] + (n - 1)*a[n - 2]}, a[n], n, z] f[z_]=(1/2)*Exponential[z + z^2/2]*(2 - Sqrt[2E pi ] Erf[1/Sqrt[2]] + Sqrt[2E pi ] Erf[(1 + z)/Sqrt[2]])
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MATHEMATICA
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a[0] = 1; a[1] = 2; a[n_] := a[n] = a[n - 1] + (n - 1)*a[n - 2] Table[a[n], {n, 0, 30}]
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CROSSREFS
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Cf. A000898, A121966, A062267, A122021, A122022.
Adjacent sequences: A122028 A122029 A122030 this_sequence A122032 A122033 A122034
Sequence in context: A114582 A091487 A143884 this_sequence A089125 A002854 A036356
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KEYWORD
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nonn
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AUTHOR
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Roger Bagula (rlbagulatftn(AT)yahoo.com), Sep 13 2006
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EXTENSIONS
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Edited by njas, Sep 17 2006
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