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A240801 Triangle read by rows: T(n,k) (n>=2, 0 <= k <= n-2) = number of possible topologies with n given vertices and n-k-2 Steiner points. 0
1, 1, 3, 3, 12, 12, 15, 75, 120, 60, 105, 630, 1350, 1200, 360, 945, 6615, 17640, 22050, 12600, 2520 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

2,3

LINKS

Table of n, a(n) for n=2..22.

E. N. Gilbert and H. O. Pollak, Steiner minimal trees, SIAM J. Appl. Math. 16, (1968), pp. 1-29. See Table 1.

EXAMPLE

Triangle begins:

1

1,3

3,12,12

15,75,120,60

105,630,1350,1200,360

945,6615,17640,22050,12600,2520

...

CROSSREFS

Row sums = A104653. A001710 and A001147 are diagonals.

Sequence in context: A065957 A303309 A268774 * A032308 A117856 A074850

Adjacent sequences:  A240798 A240799 A240800 * A240802 A240803 A240804

KEYWORD

nonn,tabl,more

AUTHOR

N. J. A. Sloane, Apr 13 2014

STATUS

approved

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Last modified November 27 01:16 EST 2021. Contains 349344 sequences. (Running on oeis4.)