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A249752 Triangle read by rows: T(n,k) = number of arrangements of n circles in the affine plane having k outer circles. 7
1, 1, 2, 3, 5, 6, 14, 52, 60, 47 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Consider the arrangements of n circles described in A250001.

T(n,k) is the number of arrangements of n circles in the affine plane whose perimeters are formed with parts from k circles. - Omar E. Pol, Aug 09 2015

From Omar E. Pol, Jul 06 2016: (Start)

Observation 1: column 1 gives A250001, at least if 1<=n<=4.

Observation 2: sum of n-th row = T(n+1,1), at least if 1<=n<=3. (End)

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

Triangle begins:

1;

1,   2;

3,   5,  6;

14, 52, 60, 47;

...

CROSSREFS

Sum of n-th row = A250001(n).

Leading diagonal gives A274702.

Cf. A252158, A261070, A274776, A274777.

Sequence in context: A131825 A289124 A304297 * A222313 A079226 A055686

Adjacent sequences:  A249749 A249750 A249751 * A249753 A249754 A249755

KEYWORD

nonn,tabl,hard,more

AUTHOR

Omar E. Pol, Dec 14 2014

EXTENSIONS

Corrected a(5)-a(6) and added a(7)-a(10) from Omar E. Pol, Oct 13 2015

STATUS

approved

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Last modified December 8 12:07 EST 2019. Contains 329862 sequences. (Running on oeis4.)