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A368813 Number of regions in a regular 2n-gon when all vertices are connect by straight lines except for the n lines joining diametrically opposite vertices. 4
0, 1, 13, 57, 171, 361, 813, 1489, 2215, 4081, 6249, 8329, 13027, 17977, 20221, 32033, 41583, 50545, 66881, 83161, 93871, 124521, 150237, 173233, 213351, 251473, 285445, 342889, 397011, 432121, 524149, 598081, 663103, 769217, 867441, 960121, 1091723, 1218889, 1333489, 1506321, 1667799 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
Table of n, a(n) for n=1..41.
Scott R. Shannon, Image for n = 2.
Scott R. Shannon, Image for n = 3.
Scott R. Shannon, Image for n = 4.
Scott R. Shannon, Image for n = 5.
Scott R. Shannon, Image for n = 6.
Scott R. Shannon, Image for n = 10.
Scott R. Shannon, Image for n = 15.
FORMULA
a(n) = A368815(n) - A368814(n) + 1 by Euler's formula.
CROSSREFS
Cf. A368814 (vertices), A368815 (edges), A368816 (k-gons), A368755, A007678.
Sequence in context: A264853 A210290 A007202 * A222161 A218593 A358303
Adjacent sequences: A368810 A368811 A368812 * A368814 A368815 A368816
KEYWORD
nonn
AUTHOR
Scott R. Shannon, Jan 06 2024
STATUS
approved

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Last modified August 31 07:15 EDT 2024. Contains 375552 sequences. (Running on oeis4.)