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A026586 Number of labeled essential directed acyclic graphs (DAGs). 0
1, 1, 1, 4, 59, 2616, 306117, 87716644, 58874478231, 90018247082416, 307775459402071913, 2322338398654088751036, 38293189001166839643861795, 1369158635491114830895696234696, 105480725505896171175318367295035341 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..14.

Bertran Steinsky, Enumeration of labelled chain graphs and labeled essential directed acyclic graphs, Discrete Mathematics, 270 (2003), 267-278.

FORMULA

a(0)=1, a(n) = Sum_{k=1..n} (-1)^(k+1) * binomial(n, k) * (2^(n-k)-n+k) * a(n-k) [from Steinsky]. - Sean A. Irvine, Oct 06 2019

CROSSREFS

Sequence in context: A264820 A194534 A331712 * A298064 A298713 A058173

Adjacent sequences:  A026583 A026584 A026585 * A026587 A026588 A026589

KEYWORD

nonn

AUTHOR

Detlef Pauly (dettodet(AT)yahoo.de), Aug 22 2003

EXTENSIONS

a(0)=1 inserted by Sean A. Irvine, Oct 06 2019

STATUS

approved

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Last modified December 5 17:28 EST 2021. Contains 349557 sequences. (Running on oeis4.)