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1, 3, 7, 16, 40, 116, 395, 1551, 6847, 33290, 175708, 996696, 6031281, 38710303, 262288647, 1868825536, 13955504572, 108907053412, 885935408411, 7495705968467, 65829634763895, 599033379716074, 5638952863115576, 54830878201599424, 549981672834888561
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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LINKS
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Alois P. Heinz, Table of n, a(n) for n = 0..500
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FORMULA
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G.f.: (1/(1 - x)^2) * Sum_{i>=0} x^i / Product_{j=1..i} (1 - j*x). - Ilya Gutkovskiy, Jun 05 2017
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MAPLE
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b:= proc(n) option remember; `if`(n>0, b(n-1), 0)+combinat[bell](n) end:
a:= proc(n) option remember; `if`(n>0, a(n-1), 0)+b(n) end:
seq(a(n), n=0..30); # Alois P. Heinz, Apr 20 2012
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MATHEMATICA
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Table[Sum[BellB[k], {k, 0, n }], {n, 0, 24}] // Accumulate (* Jean-François Alcover, Mar 13 2014 *)
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CROSSREFS
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Cf. A005001.
Sequence in context: A263316 A001698 A261236 * A009337 A036567 A018023
Adjacent sequences: A029758 A029759 A029760 * A029762 A029763 A029764
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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