A332376 Total number of edges in graph formed by the straight line segments connecting the edges of an equilateral triangle with the n-1 points resulting from a subdivision of the sides into n equal pieces.

3, 12, 39, 54, 123, 144, 255, 282, 435, 468, 663, 702, 939, 984, 1245, 1314, 1635, 1692, 2055, 2100, 2523, 2592, 3039, 3042, 3603, 3684, 4215, 4302, 4875, 4950, 5583, 5682, 6339, 6444, 7107, 7254, 7995, 8112, 8895, 8964, 9843, 9936, 10839, 10974

Offset

1,1

Links

N. J. A. Sloane, Table of n, a(n) for n = 1..1000

Formula

a(n) = A092098(n) + A331782(n) - 1 (Euler's formula).

Crossrefs

Cf. A091908, A092098 (number of cells), A331782 (number of vertices).

Equals three times A332377.

Sequence in context: A222643 A129014 A335412 * A379013 A341712 A261384

Adjacent sequences: A332373 A332374 A332375 * A332377 A332378 A332379

Keyword

nonn

Author

N. J. A. Sloane, Feb 13 2020

Status

approved