A375480 - OEIS

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A375480

For any n > 0, let L_n be the set of straight lines passing through the points (i, a(i)) and (j, a(j)) for i < j <= n; a(1) = a(2) = 0, and then a(n) is the number of elements in L_{n-1} that are not is L_{n-2}.

2

0, 0, 1, 2, 1, 4, 2, 6, 3, 6, 7, 8, 8, 9, 7, 12, 9, 14, 12, 14, 15, 12, 15, 16, 8, 20, 17, 21, 23, 22, 18, 28, 25, 25, 31, 23, 33, 26, 29, 28, 39, 32, 30, 34, 29, 37, 41, 39, 43, 42, 31, 42, 33, 44, 38, 47, 50, 52, 39, 47, 49, 48, 44, 53, 61, 51, 59, 55, 56

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

LINKS

Table of n, a(n) for n=1..69.

Rémy Sigrist, PARI program

EXAMPLE

The first terms, alongside the corresponding new lines, are:

n a(n) Lines

- ---- --------------------------------------------------------

1 0 {}

2 0 {}

3 1 {0}

4 2 {1/2*x-1/2, x-2}

5 1 {2/3*x-2/3}

6 4 {1/4*x-1/4, 1/3*x-2/3, 1, -x+6}

7 2 {4/5*x-4/5, 3*x-14}

8 6 {1/3*x-1/3, 2/5*x-4/5, 1/4*x+1/4, 2, 1/2*x-3/2, -2*x+16}

9 3 {6/7*x-6/7, 5/3*x-22/3, 4*x-26}

PROG

(PARI) \\ See Links section.

CROSSREFS

Sequence in context: A349442 A130742 A130107 * A107130 A194747 A065423

Adjacent sequences: A375477 A375478 A375479 * A375481 A375482 A375483

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Aug 17 2024

STATUS

approved