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%I #20 Apr 28 2020 06:37:18
%S 7,29,89,201,387,641,1067,1599,2305,3233,4431,5855,7721,9853,12369,
%T 15477,19093,23141,28073,33557,39699,46773,54815,63681,73825,84833,
%U 97005,110579,125587,141733,160063,179913,201105,224409,249329,276215,305925,337345,370793
%N 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.
%C Same as A331763, but only count interior crossings.
%C See A331452 for other illustrations.
%H Lars Blomberg, <a href="/A331767/b331767.txt">Table of n, a(n) for n = 1..100</a>
%H Scott R. Shannon, <a href="/A331452/a331452_13.png">Colored illustration for a(3) = 89.</a>
%Y Cf. A331763, A331765, A331766.
%K nonn
%O 1,1
%A _Scott R. Shannon_ and _N. J. A. Sloane_, Feb 05 2020
%E Needs to be extended using the new data for A331763. - _N. J. A. Sloane_, Mar 12 2020
%E a(10) and beyond from _Lars Blomberg_, Apr 28 2020
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