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a(n) is the number of distinct lines created inside an n-gon when connecting vertex k to vertex 2k mod n.
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%I #11 Jan 03 2022 21:23:18

%S 0,1,2,2,4,5,5,7,8,8,10,11,11,13,14,14,16,17,17,19,20,20,22,23,23,25,

%T 26,26,28,29,29,31,32,32,34,35,35,37,38,38,40,41,41,43,44,44,46,47,47,

%U 49,50,50,52,53,53,55,56,56,58,59,59,61,62,62,64,65,65

%N a(n) is the number of distinct lines created inside an n-gon when connecting vertex k to vertex 2k mod n.

%C See A335057 for illustrations.

%F a(n) = n - 3 - A079978(n).

%F a(3) = 0, a(n) = n - 4 + sign(n mod 3) for n>=4. - _Wesley Ivan Hurt_, Dec 29 2021

%Y Cf. A079978.

%Y Cf. A335057 (regions), A335058 (edges), A335059 (vertices).

%K nonn

%O 3,3

%A _Lars Blomberg_, May 24 2020