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%I #16 May 05 2016 10:54:42
%S 3,5,8,12,17
%N a(n) = greatest number of edges in a simple polygon on an n X n grid with no two edges parallel.
%C Worthy of consideration to introduce slopes in the math classroom.
%C a(7) >= 23 and a(8) >= 29, see illustration in Links.
%H Hiroaki Yamanouchi, <a href="/A255981/a255981.pdf">Examples</a>
%H Giovanni Resta, <a href="/A255981/a255981.png">Illustration of a(7)>=23 and a(8)>=29</a>
%e a(3) = 5 because of this quadrilateral in a 3 x 3 square:
%e 1 2 .
%e . 4 .
%e 5 . 3
%e a(4) = 8 because of this polygon:
%e 1 3 . 4
%e . . 2 6
%e . . 5 7
%e . 8 . .
%Y Cf. A271449. Construction perhaps related to construction of Costas arrays: A008404.
%K nonn,more
%O 2,1
%A _Gordon Hamilton_, Mar 13 2015
%E a(5)-a(6) corrected by _Hiroaki Yamanouchi_, Mar 14 2015
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