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Search: id:A145456
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| 1, 0, 0, 0, 0, 0, 1, 7, 28, 84, 210, 462, 1386, 13728, 171171, 1686685, 13461448, 91495768, 551777772, 3142726692, 19787406360, 172188951144, 1999835600301, 24655331721867, 285725747201356, 3034790658153100, 29876851476502030
(list; graph; listen)
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OFFSET
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0,8
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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 6 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 6 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, 6) *a(n-j), j=1..n)) end: seq (a(n), n=0..30);
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CROSSREFS
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Cf. 6th column of A145460, A143398.
Sequence in context: A000579 A049017 A019501 this_sequence A145135 A144900 A054469
Adjacent sequences: A145453 A145454 A145455 this_sequence A145457 A145458 A145459
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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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