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A333033
Number of quadrilateral regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition),
4
0, 0, 24, 102, 252, 504, 867, 1431, 2214, 3228, 4509, 6237, 8481, 11259, 14445, 18261, 22935, 28497, 34980, 42762, 51708, 61632, 72795, 85791, 100611, 117027, 134874, 154836, 177402, 202548, 230355, 261543, 295707, 332271, 371313, 413937, 460881, 511551
OFFSET
1,3
COMMENTS
See A328526 for images of the triangular frame.
LINKS
CROSSREFS
Cf. A328526 (regions), A333030 (edges), A333031 (vertices), A333032 (3-gons), A331776 (square frame), A274586 (filled triangle).
Sequence in context: A297798 A048529 A213842 * A269047 A182675 A100155
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(12) and beyond from Lars Blomberg, May 01 2020
STATUS
approved