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A001862 Number of forests of least height with n nodes.
(Formerly M1773 N0702)
1
1, 1, 2, 7, 26, 111, 562, 3151, 19252, 128449, 925226, 7125009, 58399156, 507222535, 4647051970, 44747776651, 451520086208, 4761032807937, 52332895618066, 598351410294193, 7102331902602676, 87365859333294151, 1111941946738682522, 14621347433458883187 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983. See (3.3.7): number of ways to cover the complete graph K_n with star graphs.

J. Riordan, Forests of labeled trees, J. Combin. Theory, 5 (1968), 90-103.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe, Table of n, a(n) for n = 0..100

J. Riordan, Letter to N. J. A. Sloane, Oct. 1970

John Riordan and N. J. A. Sloane, Correspondence, 1974

FORMULA

E.g.f.: exp(x*(exp(x)-x/2)).

MATHEMATICA

Range[0, 20]! CoefficientList[Series[Exp[x Exp[x] - x^2/2], {x, 0, 20}], x] (* Geoffrey Critzer, Mar 13 2011 *)

CROSSREFS

Sequence in context: A150586 A196709 A150587 * A150588 A150589 A007168

Adjacent sequences:  A001859 A001860 A001861 * A001863 A001864 A001865

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Formula and more terms from Vladeta Jovovic, Mar 27 2001

STATUS

approved

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Last modified January 22 19:00 EST 2019. Contains 319365 sequences. (Running on oeis4.)