A333031 Number of vertices in an equilateral triangle "frame" of size n (see Comments in A328526 for definition).

3, 10, 58, 183, 408, 777, 1323, 2142, 3276, 4773, 6717, 9264, 12507, 16554, 21351, 27090, 34047, 42318, 52008, 63453, 76566, 91371, 108249, 127608, 149487, 173982, 201072, 231225, 265002, 302487, 343857, 389856, 440175, 494670, 553611, 617610, 687477, 763320

Offset

1,1

Comments

For n<=3 the terms equal A274585(n). 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), A333032 (3-gons), A333033 (4-gons), A331776 (square frame), A274586 (filled triangle).

Sequence in context: A307906 A366696 A274585 * A242953 A112101 A159321

Adjacent sequences: A333028 A333029 A333030 * A333032 A333033 A333034

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