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Search: id:A143979
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| A143979 |
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Rectangular array R by antidiagonals: label each unit square in the 1st quadrant lattice by its northeast vertex (x,y) and mark squares having |x-y|=0(mod 3); then R(m,n) is the number of UNmarked squares in the rectangle [0,m]x[0,n]. |
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+0
4
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| 0, 1, 1, 2, 2, 2, 2, 4, 4, 2, 3, 5, 6, 5, 3, 4, 6, 8, 8, 6, 4, 4, 8, 10, 10, 10, 8, 4, 5, 9, 12, 13, 13, 12, 9, 5, 6, 10, 14, 16, 16, 16, 14, 10, 6, 6, 12, 16, 18, 20, 20, 18, 16, 12, 6, 7, 13, 18, 21, 23, 24, 23, 21, 18, 13, 7, 8, 14, 20, 24, 26, 28, 28, 26, 24, 20, 14, 8, 8, 16, 22, 26, 30
(list; table; graph; listen)
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OFFSET
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1,4
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COMMENT
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Rows numbered 3,6,9,12,15,... are, except for initial terms, multiples of (1,2,3,4,5,6,7,...)=A000027.
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FORMULA
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R(m,n)=mn-Floor(2mn/3).
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EXAMPLE
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Northwest corner:
0 1 2 2 3 4 4
1 2 4 5 6 8 9
2 4 6 8 10 12 14
2 5 8 10 13 16 18
3 6 10 13 16 20 23
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CROSSREFS
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Cf. A143974, A143976, A143977.
Sequence in context: A007457 A119802 A060369 this_sequence A034877 A023161 A023155
Adjacent sequences: A143976 A143977 A143978 this_sequence A143980 A143981 A143982
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KEYWORD
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nonn,tabl
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), Sep 06 2008
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