A386561 Place a point on the integer coordinates, up to |n|, along all four axial directions on a Cartesian plane, and then join an infinite straight line between every pair of points: a(n) is the number of finite edges created in the resulting graph.

8, 136, 804, 2608, 6568, 13396, 26556, 45120, 73060, 110984, 171144, 238900, 344212, 462788, 607384, 786476, 1037772, 1293904, 1654432, 2013768, 2447312, 2965392

Offset: 1

Author

Scott R. Shannon, Jul 26 2025

Keywords

• nonn
• more

Comments

See A386559 and A386560 for images of the graphs.

Crossrefs

Cf. A386559 (vertices), A386560 (regions), A386562 (k-gons), A347751, A344899, A344896, A345650.

Formula

a(n) = A386559(n) + A386560(n) - 1 by Euler's formula.