login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A177726 Number of line segments connecting exactly 10 points in an n x n grid of points 0
0, 0, 0, 0, 0, 0, 0, 0, 0, 22, 52, 90, 136, 190, 252, 322, 400, 486, 620, 770, 936, 1118, 1316, 1530, 1760, 2006, 2268, 2662, 3088, 3546, 4036, 4558, 5112, 5698, 6316, 6966, 7800, 8682, 9612, 10590, 11616, 12690, 13812, 14982, 16200, 17842, 19564, 21366 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,10

COMMENTS

a(n) is also the number of pairs of points visible to each other exactly through 8 points in an n x n grid of points.

LINKS

Table of n, a(n) for n=1..48.

S. Mustonen, On lines going through a given number of points in a rectangular grid of points

FORMULA

See Mathematica code.

MATHEMATICA

j=9;

a[n_]:=a[n]=If[n<=j, 0, 2*a1[n]-a[n-1]+R1[n]]

a1[n_]:=a1[n]=If[n<=j, 0, 2*a[n-1]-a1[n-1]+R2[n]]

R1[n_]:=R1[n]=If[n<=j, 0, R1[n-1]+4*S[n]]

R2[n_]:=(n-1)*S[n]

S[n_]:=If[Mod[n-1, j]==0, EulerPhi[(n-1)/j], 0]

Table[a[n], {n, 1, 50}]

CROSSREFS

Sequence in context: A200880 A111576 A277979 * A101571 A122502 A244212

Adjacent sequences:  A177723 A177724 A177725 * A177727 A177728 A177729

KEYWORD

nonn

AUTHOR

Seppo Mustonen, May 13 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified March 29 13:11 EDT 2017. Contains 284270 sequences.