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Search: id:A052882
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| A052882 |
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A simple grammar: rooted ordered set partitions. |
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+0 11
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| 0, 1, 2, 9, 52, 375, 3246, 32781, 378344, 4912515, 70872610, 1124723193, 19471590876, 365190378735, 7376016877334, 159620144556645, 3684531055645648, 90366129593683035, 2346673806524446218
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Recurrence (see Mathematica line) is similar to that for Genocchi numbers A001469 - Wouter Meeussen (wouter.meeussen(AT)pandora.be), Jan 09 2001
Stirling transform of A024167(n)=[1,1,5,14,94,...] is a(n)=[1,2,9,52,375,...]. - Michael Somos Mar 04 2004
Stirling transform of a(n)=[0,2,9,52,375,...] is A087301(n+1)=[0,2,3,20,...]. - Michael Somos Mar 04 2004
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LINKS
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INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 855
S. Ramanujan, Notebook entry
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FORMULA
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E.g.f.: x/(2-exp(x)).
a(n) = (1/2)*sum(k=0, n-1, B_k*A000629(k)*binomial(n, k)) where B_k is the k-th Bernoulli number. - Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 19 2005
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MAPLE
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spec := [S, {C=Sequence(B), B=Set(Z, 1 <= card), S=Prod(Z, C)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
with(combinat):a:=n->sum(sum(sum((-1)^(k-i)*binomial(k, i)*i^n, i=0..n), k=0..n), m=0..n): seq(a(n), n=-1..17); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 03 2007
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MATHEMATICA
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a[1] := 1; a[n_] := a[n]=Sum[ Binomial[n, m] a[ n-m], {m, 1, n-1}]
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PROGRAM
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(PARI) a(n)=if(n<0, 0, n!*polcoeff(subst(x/(1-y), y, exp(x+x*O(x^n))-1), n))
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CROSSREFS
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Cf. A001469.
For n>0, a(n)=n*A000670(n).
Sequence in context: A069271 A006152 A143508 this_sequence A143922 A110322 A161631
Adjacent sequences: A052879 A052880 A052881 this_sequence A052883 A052884 A052885
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KEYWORD
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easy,nonn
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AUTHOR
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encyclopedia(AT)pommard.inria.fr, Jan 25 2000
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