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A123551 Triangle read by rows: T(n,k) gives number of unlabeled graphs without endpoints on n nodes and k edges, (n >= 0, 0 <= k <= n(n-1)/2). 2
1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 2, 4, 3, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 8, 13, 16, 13, 8, 5, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 10, 22, 48, 76, 97, 102, 84, 60, 39, 20, 10, 5, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 10, 25, 64, 152, 331, 617, 930, 1173, 1253, 1140 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,21

REFERENCES

R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1977.

LINKS

R. W. Robinson, Rows 0 through 16, flattened

FORMULA

T(n,k) = A008406(n,k) - A240168(n,k). - Andrew Howroyd, Apr 16 2021

EXAMPLE

Triangle begins:

n = 0

k = 0 : 1

******************** total (n = 0) = 1

n = 1

k = 0 : 1

******************** total (n = 1) = 1

n = 2

k = 0 : 1

k = 1 : 0

******************** total (n = 2) = 1

n = 3

k = 0 : 1

k = 1 : 0

k = 2 : 0

k = 3 : 1

******************** total (n = 3) = 2

n = 4

k = 0 : 1

k = 1 : 0

k = 2 : 0

k = 3 : 1

k = 4 : 1

k = 5 : 1

k = 6 : 1

******************** total (n = 4) = 5

CROSSREFS

Row sums are A004110.

Cf. A008406, A240168.

Sequence in context: A307500 A049245 A123547 * A286275 A029717 A135567

Adjacent sequences:  A123548 A123549 A123550 * A123552 A123553 A123554

KEYWORD

nonn,tabf

AUTHOR

N. J. A. Sloane, Nov 14 2006

STATUS

approved

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Last modified September 25 02:00 EDT 2021. Contains 347651 sequences. (Running on oeis4.)