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A122078 Triangle read by rows: T(n,k) is the number of unlabeled acyclic digraphs with n >= 0 nodes and n-k outnodes (0 <= k <= n). 14
1, 1, 0, 1, 1, 0, 1, 2, 3, 0, 1, 3, 11, 16, 0, 1, 4, 25, 108, 164, 0, 1, 5, 47, 422, 2168, 3341, 0, 1, 6, 78, 1251, 15484, 88747, 138101, 0, 1, 7, 120, 3124, 79836, 1215783, 7409117, 11578037, 0, 1, 8, 174, 6925, 333004, 11620961, 199203464, 1252610909, 1961162564, 0 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
0,8
REFERENCES
R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..495 (rows 0..30; rows 0..15 from R. W. Robinson)
Andrew Howroyd, PARI program, Dec 2021, updated Jan 2022.
EXAMPLE
Triangle T(n,k) begins:
1:
1, 0;
1, 1, 0;
1, 2, 3, 0;
1, 3, 11, 16, 0;
1, 4, 25, 108, 164, 0;
1, 5, 47, 422, 2168, 3341, 0;
1, 6, 78, 1251, 15484, 88747, 138101, 0;
...
PROG
(PARI) \\ See link for program code.
{ my(T=AcyclicDigraphsByNonSources(8)); for(n=1, #T, print(T[n])) } \\ Andrew Howroyd, Dec 31 2021
CROSSREFS
Row sums give A003087.
Diagonals include A000007, A350415.
Cf. A058876 (labeled case), A350447, A350448, A350449, A350450.
Sequence in context: A340986 A340798 A355427 * A292783 A320354 A285320
KEYWORD
nonn,tabl
AUTHOR
N. J. A. Sloane, Oct 18 2006
EXTENSIONS
Zero terms inserted by Andrew Howroyd, Dec 29 2021
STATUS
approved

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Last modified February 24 12:51 EST 2024. Contains 370303 sequences. (Running on oeis4.)