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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

See A328526 for images of the triangular frame.

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..65

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

Adjacent sequences:  A333030 A333031 A333032 * A333034 A333035 A333036

KEYWORD

nonn

AUTHOR

Scott R. Shannon and N. J. A. Sloane, Mar 05 2020

EXTENSIONS

a(12) and beyond from Lars Blomberg, May 01 2020

STATUS

approved

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Last modified October 18 16:29 EDT 2021. Contains 348068 sequences. (Running on oeis4.)