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A358328 Triangle read by rows: T(n,k) is the number of polygons with 2*n sides, of which k run through the center of a circle, on the circumference of which the 2*n vertices of the polygon are arranged at equal spacing, up to rotation.

%I A358328 #22 Dec 05 2022 04:40:53
%S A358328 0,0,1,1,0,1,4,4,4,2,98,120,84,24,6,5648,6912,4032,1344,288,40,532344,
%T A358328 631680,351360,118408,26400,3840,322,72724122,84211200,45907200,
%U A358328 15436800,3513600,552960,57600,3294,13577195574,15432560640,8305920000,2786273280,643507200,106122240,12418560,967680,40320
%N A358328 Triangle read by rows: T(n,k) is the number of polygons with 2*n sides, of which k run through the center of a circle, on the circumference of which the 2*n vertices of the polygon are arranged at equal spacing, up to rotation.
%C A358328 By "2*n-sided polygons" we mean the polygons that can be drawn by connecting 2*n equally spaced points on a circle.
%C A358328 T(0,0)=0 and T(0,1)=1 by convention.
%C A358328 The sequence is limited to even-sided polygons, since all odd-sided polygons have no side passing through the center.
%H A358328 Ludovic Schwob, <a href="/A358328/b358328.txt">Table of n, a(n) for n = 0..5150</a>
%e A358328 Triangle begins:
%e A358328     0;
%e A358328     0,   1;
%e A358328     1,   0,   1;
%e A358328     4,   4,   4,   2;
%e A358328    98, 120,  84,  24,   6;
%Y A358328 Row sums give A094155(n).
%Y A358328 Cf. A330662.
%K A358328 nonn,tabl
%O A358328 0,7
%A A358328 _Ludovic Schwob_, Nov 09 2022