A333033 Number of quadrilateral regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition),

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

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