

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)=mnFloor(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



