A333032 Number of triangular regions in an equilateral triangular "frame" of size n (see Comments in A328526 for definition),

1, 12, 48, 147, 291, 519, 879, 1383, 2079, 3039, 4359, 5991, 7983, 10515, 13731, 17571, 22131, 27543, 33951, 41271, 49599, 59355, 70779, 83499, 97611, 113763, 132243, 152619, 175035, 199707, 226827, 256443, 288747, 324603, 364395, 407139, 452979, 503319

Offset

1,2

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), A333033 (4-gons), A331776 (square frame), A274586 (filled triangle).

Sequence in context: A292022 A265040 A059162 * A190622 A117027 A161171

Adjacent sequences: A333029 A333030 A333031 * A333033 A333034 A333035

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