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A008893 Equilateral triangles in hexagonal chunk of side n in hexagonal lattice. 2
0, 8, 66, 258, 710, 1590, 3108, 5516, 9108, 14220, 21230, 30558, 42666, 58058, 77280, 100920, 129608, 164016, 204858, 252890, 308910, 373758, 448316, 533508, 630300, 739700, 862758, 1000566, 1154258, 1325010, 1514040, 1722608, 1952016, 2203608, 2478770 (list; graph; refs; listen; history; internal format)
OFFSET

0,2

COMMENTS

The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 0..10000

G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2

FORMULA

a(n) = n*(n+1)*(7*n^2+7*n+2)/4.

G.f.: -2*x*(4*x^2+13*x+4)/(x-1)^5 [From Maksym Voznyy (voznyy(AT)mail.ru), Aug 10 2009]

CROSSREFS

Cf. A152041.

Sequence in context: A041114 A015496 A039329 * A168302 A121782 A121781

Adjacent sequences:  A008890 A008891 A008892 * A008894 A008895 A008896

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy

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Last modified February 14 23:53 EST 2012. Contains 205689 sequences.