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A007563
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Number of rooted connected graphs where every block is a complete graph.
(Formerly M2751)
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7
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0, 1, 1, 3, 8, 25, 77, 258, 871, 3049, 10834, 39207, 143609, 532193, 1990163, 7503471, 28486071, 108809503, 417862340, 1612440612, 6248778642, 24309992576, 94905791606, 371691137827, 1459935388202, 5749666477454
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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REFERENCES
| F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 71, (3.4.13).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=0..200
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210.
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 167
N. J. A. Sloane, Transforms
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FORMULA
| Shifts left when Euler transform applied twice.
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MAPLE
| with (numtheory): etr:= proc(p) local b; b:= proc(n) option remember; if n=0 then 1 else (add (d*p(d), d=divisors(n)) +add (add(d*p(d), d=divisors(j)) *b(n-j), j=1..n-1))/n fi end end: b:= etr(a): c:= etr(b): a:= n-> if n=0 then 0 else c(n-1) fi: seq (a(n), n=0..25); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Sep 06 2008]
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CROSSREFS
| Cf. A007549, A030019, A035051-A035053.
Sequence in context: A148790 A148791 A148792 * A050383 A060404 A192905
Adjacent sequences: A007560 A007561 A007562 * A007564 A007565 A007566
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KEYWORD
| nonn,nice,eigen
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| New description from Christian G. Bower (bowerc(AT)usa.net), Oct 15 1998.
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