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%I #49 Dec 26 2016 13:40:10
%S 1,3,5,7,9,9,9,9,11,13,13,15,17,19,21,23,25,27,27,27,27,27,27,27,29,
%T 31,33,33,33,35,37,39,41,43,45,47,49,51,53,53,53,53,53,53,53,53,53,53,
%U 55,57,59,61
%N Square spiral reflection.
%C Draw a square spiral growing by a unit line segment on each step, and at the same time, draw another square spiral in the opposite direction (again using a unit line segment) that turns after the first step (see example). a(n) is the number of unit line segments remaining after the n-th step. Note that overlapping line segments are counted once.
%e __ ____ ____ ____ ____ ____
%e __ __| __| __| | __| | __| | __| | __|
%e | __| ____| |____| |____| |____| |____|
%e n=1 n=2 n=3 n=4 n=5 n=6 n=7 n=8
%e --
%e __ __ __
%e ________ ____ __ ____ __ ____ __| ____ __| ____ __|
%e | __| | __| | | __| | | __| | | __| | | __| |
%e |____|__ |____|__| |____|__| |____|__| |____|__| |____|__|
%e | __| __ __|
%e n=9 n=10 n=11 n=12 n=13 n=14
%K nonn
%O 1,2
%A _Wesley Ivan Hurt_, Dec 25 2016
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