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A295707 Square array A(n,k), n >= 1, k >= 1, read by antidiagonals, where A(n,k) is the number of lines through at least 2 points of an n X k grid of points. 10
0, 1, 1, 1, 6, 1, 1, 11, 11, 1, 1, 18, 20, 18, 1, 1, 27, 35, 35, 27, 1, 1, 38, 52, 62, 52, 38, 1, 1, 51, 75, 93, 93, 75, 51, 1, 1, 66, 100, 136, 140, 136, 100, 66, 1, 1, 83, 131, 181, 207, 207, 181, 131, 83, 1, 1, 102, 164, 238, 274, 306, 274, 238, 164, 102, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,5

LINKS

Seiichi Manyama, Antidiagonals n = 1..140, flattened

S. Mustonen, On lines and their intersection points in a rectangular grid of points

FORMULA

A(n,k) = (1/2) * (f(n,k,1) - f(n,k,2)), where f(n,k,m) = Sum ((n-|m*x|)*(k-|m*y|)); -n < m*x < n, -k < m*y < k, (x,y)=1.

EXAMPLE

Square array begins:

   0,  1,  1,   1,   1, ...

   1,  6, 11,  18,  27, ...

   1, 11, 20,  35,  52, ...

   1, 18, 35,  62,  93, ...

   1, 27, 52,  93, 140, ...

   1, 38, 75, 136, 207, ...

CROSSREFS

Columns k=2..9 give A160842, A160843, A160844, A160845, A160846, A160847, A160848, A160849, A160850.

Main diagonal gives A018808. Reading up to the diagonal gives A107348.

Sequence in context: A046617 A131063 A081579 * A146772 A202868 A202877

Adjacent sequences:  A295703 A295704 A295705 * A295708 A295709 A295710

KEYWORD

nonn,tabl

AUTHOR

Seiichi Manyama, Nov 26 2017

STATUS

approved

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Last modified February 23 00:33 EST 2018. Contains 299473 sequences. (Running on oeis4.)