A057276 - OEIS

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A057276

Triangle T(n,k) of number of strongly connected digraphs on n unlabeled nodes and with k arcs, k=0..n*(n-1).

1, 0, 0, 1, 0, 0, 0, 1, 2, 1, 1, 0, 0, 0, 0, 1, 4, 16, 22, 22, 11, 5, 1, 1, 0, 0, 0, 0, 0, 1, 7, 58, 240, 565, 928, 1065, 953, 640, 359, 150, 59, 16, 5, 1, 1, 0, 0, 0, 0, 0, 0, 1, 10, 165, 1281, 6063, 19591, 47049, 87690, 131927, 163632, 170720, 151238, 115122, 75357, 42745, 20891, 8877, 3224, 1039, 286, 76, 17, 5, 1, 1

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,9

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..2680 (rows 1..20)

EXAMPLE

Triangle begins:

[1] 1;

[2] 0,0,1;

[3] 0,0,0,1,2,1,1;

[4] 0,0,0,0,1,4,16,22,22,11,5,1,1;

...

The number of strongly connected digraphs on 3 unlabeled nodes is 5 = 1+2+1+1.

PROG

(PARI) \\ See PARI link in A350489 for program code.

{ my(A=A057276rows(5)); for(n=1, #A, print(A[n])) } \\ Andrew Howroyd, Jan 13 2022

CROSSREFS

Row sums give A035512.

Column sums give A350752.

The labeled version is A057273.

Cf. A054733, A057270, A057277, A057278, A057279, A350489.

Sequence in context: A025923 A351358 A138158 * A259829 A035185 A339659

Adjacent sequences: A057273 A057274 A057275 * A057277 A057278 A057279

KEYWORD

nonn,tabf

AUTHOR

Vladeta Jovovic, Goran Kilibarda, Sep 14 2000

EXTENSIONS

Terms a(46) and beyond from Andrew Howroyd, Jan 13 2022

STATUS

approved