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A003025 Number of n-node labeled acyclic digraphs with 1 out-point.
(Formerly M2083)
5
1, 2, 15, 316, 16885, 2174586, 654313415, 450179768312, 696979588034313, 2398044825254021110, 18151895792052235541515, 299782788128536523836784628, 10727139906233315197412684689421 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.

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

LINKS

Table of n, a(n) for n=1..13.

EXAMPLE

a(2) = 2: o-->--o (2 ways)

a(3) = 15: o-->--o-->--o (6 ways) and

o ... o o-->--o

.\ . / . \ . /

. v v ... v v

.. o ..... o

(3 ways) (6 ways)

CROSSREFS

Cf. A058876, A003026.

Sequence in context: A304120 A255929 A059167 * A015200 A030642 A297077

Adjacent sequences:  A003022 A003023 A003024 * A003026 A003027 A003028

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Vladeta Jovovic, Apr 10 2001

STATUS

approved

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Last modified October 13 20:38 EDT 2019. Contains 327981 sequences. (Running on oeis4.)