login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A350731 Triangle read by rows: T(n,k) is the number of strongly connected oriented graphs on n labeled nodes with k arcs, n >= 1, k=0..n*(n-1)/2. 5
1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 6, 36, 24, 0, 0, 0, 0, 0, 24, 480, 1940, 2970, 2040, 544, 0, 0, 0, 0, 0, 0, 120, 5040, 51330, 221910, 527940, 772080, 722250, 426420, 146160, 22320, 0, 0, 0, 0, 0, 0, 0, 720, 52920, 1026060, 8810970, 43268442, 138984510 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1350 (rows 1..20)

EXAMPLE

Triangle begins:

[1] 1;

[2] 0, 0;

[3] 0, 0, 0, 2;

[4] 0, 0, 0, 0, 6, 36, 24;

[5] 0, 0, 0, 0, 0, 24, 480, 1940, 2970, 2040, 544;

...

PROG

(PARI)

OrientedGgf(n, y=1) = {sum(k=0, n, ((1+2*y)/(1+y))^(k*(k-1)/2)*x^k/k!, O(x*x^n) )}

StrongO(n, y=1) = {my(g=serconvol(1/OrientedGgf(n, y), sum(k=0, n, x^k*(1+y)^(k*(k-1)/2), O(x*x^n)))); Vec(serlaplace(-log(g)))}

row(n)={Vecrev(StrongO(n, 'y)[n], n*(n-1)/2+1)}

{ for(n=1, 6, print(row(n))) }

CROSSREFS

Row sums are A350730.

The unlabeled version is A350750.

Cf. A057273 (digraphs), A350732 (weakly connected).

Sequence in context: A011992 A318329 A107503 * A184366 A230614 A230730

Adjacent sequences: A350728 A350729 A350730 * A350732 A350733 A350734

KEYWORD

nonn,tabf

AUTHOR

Andrew Howroyd, Jan 11 2022

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 8 09:39 EST 2023. Contains 360138 sequences. (Running on oeis4.)