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Search: id:A145455
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| 1, 0, 0, 0, 0, 1, 6, 21, 56, 126, 378, 3234, 34056, 289575, 2020018, 12237225, 70634928, 468041756, 4190274648, 45557515620, 499503011496, 5121432107757, 49183015347774, 462331794763069, 4579813478536296, 50959878972009546
(list; graph; listen)
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OFFSET
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0,7
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COMMENT
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a(n) is the number of ways of placing n labeled balls into indistinguishable boxes, where in each filled box 5 balls are seen at the top.
a(n) is also the number of forests of labeled rooted trees of height at most 1, with n labels, where each root contains 5 labels.
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LINKS
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N. J. A. Sloane, Transforms
Index entries for sequences related to rooted trees
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MAPLE
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a:= proc(n) option remember; local j; `if` (n=0, 1, add (binomial (n-1, j-1) *binomial(j, 5) *a(n-j), j=1..n)) end: seq (a(n), n=0..30);
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CROSSREFS
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Cf. 5th column of A145460, A143398.
Sequence in context: A100356 A137361 A058484 this_sequence A145134 A074745 A056414
Adjacent sequences: A145452 A145453 A145454 this_sequence A145456 A145457 A145458
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KEYWORD
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nonn
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AUTHOR
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Alois P. Heinz (heinz(AT)hs-heilbronn.de), Oct 10 2008
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