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A143976 Rectangular array R by antidiagonals: label each unit square in the first quadrant lattice by its northeast vertex (x,y) and mark squares having x+y=1(mod 3); then R(m,n) is the number of UNmarked squares in the rectangle [0,m]x[0,n]. 2
1, 2, 2, 2, 3, 2, 3, 4, 4, 3, 4, 6, 6, 6, 4, 4, 7, 8, 8, 7, 4, 5, 8, 10, 11, 10, 8, 5, 6, 10, 12, 14, 14, 12, 10, 6, 6, 11, 14, 16, 17, 16, 14, 11, 6, 7, 12, 16, 19, 20, 20, 19, 16, 12, 7, 8, 14, 18, 22, 24, 24, 24, 22, 18, 14, 8, 8, 15, 20, 24, 27, 28, 28, 27, 24, 20, 15, 8, 9, 16, 22, 27 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Rows: A004523, A004772, A005843, A047399, et al.

Rows numbered 3,6,9,12,15,... are, except for initial

terms, multiples of (1,2,3,4,5,6,7,...)=A000027.

LINKS

Table of n, a(n) for n=1..82.

FORMULA

R(m,n)=mn-Floor(mn/3).

EXAMPLE

Northwest corner:

1 2 2 3 4 4 5

2 3 4 6 7 8 10

2 4 6 8 10 12 14

3 6 8 1 14 16 18

4 7 10 14 17 20 24

See A143974.

CROSSREFS

Cf. A143974, A143977, A143979.

Sequence in context: A165015 A178994 A306608 * A194296 A194336 A127159

Adjacent sequences:  A143973 A143974 A143975 * A143977 A143978 A143979

KEYWORD

nonn,tabl

AUTHOR

Clark Kimberling, Sep 06 2008

STATUS

approved

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Last modified July 20 05:43 EDT 2019. Contains 325168 sequences. (Running on oeis4.)