A331767 Number of interior vertices formed by drawing the lines connecting any two of the 2*(n+2) perimeter points of a 3 X (n+1) square grid.

7, 29, 89, 201, 387, 641, 1067, 1599, 2305, 3233, 4431, 5855, 7721, 9853, 12369, 15477, 19093, 23141, 28073, 33557, 39699, 46773, 54815, 63681, 73825, 84833, 97005, 110579, 125587, 141733, 160063, 179913, 201105, 224409, 249329, 276215, 305925, 337345, 370793

Offset

1,1

Comments

Same as A331763, but only count interior crossings.

See A331452 for other illustrations.

Links

Lars Blomberg, Table of n, a(n) for n = 1..100

Scott R. Shannon, Colored illustration for a(3) = 89.

Crossrefs

Cf. A331763, A331765, A331766.

Sequence in context: A242727 A229795 A114043 * A166189 A001779 A257201

Adjacent sequences: A331764 A331765 A331766 * A331768 A331769 A331770

Keyword

nonn

Author

Scott R. Shannon and N. J. A. Sloane, Feb 05 2020

Extensions

Needs to be extended using the new data for A331763. - N. J. A. Sloane, Mar 12 2020

a(10) and beyond from Lars Blomberg, Apr 28 2020

Status

approved