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Search: id:A007550
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| A007550 |
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Natural numbers exponentiated twice.
(Formerly M3568)
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+0
1
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| 1, 4, 20, 127, 967, 8549, 85829, 962308, 11895252, 160475855, 2343491207, 36795832297, 617662302441, 11031160457672, 208736299803440, 4169680371133507, 87648971646028515, 1933298000313801349
(list; graph; listen)
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OFFSET
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1,2
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LINKS
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M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210.
N. J. A. Sloane, Transforms
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 166
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FORMULA
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E.g.f.: exp G(x), where G(x) = exp(x*exp(x)) = e.g.f. for A000248.
a(n) = sum( k^(n - k) binomial(n,k) bell(k), k = 0..n ) - Olivier GERARD (olivier.gerard(AT)gmail.com), Oct 24 2007
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MAPLE
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exptr:= proc (p) local g; g:= proc(n) option remember; p(n) +add (binomial (n-1, k-1) *p(k) *g(n-k), k=1..n-1) end: end: a:= exptr (exptr (n->n)): seq (a(n), n=1..30); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Oct 07 2008]
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CROSSREFS
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Sequence in context: A002793 A151341 A135886 this_sequence A080795 A126674 A082032
Adjacent sequences: A007547 A007548 A007549 this_sequence A007551 A007552 A007553
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KEYWORD
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nonn,nice
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AUTHOR
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njas.
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