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A171972 Integer part of the surface area of a regular tetrahedron with edge length n. 7
1, 6, 15, 27, 43, 62, 84, 110, 140, 173, 209, 249, 292, 339, 389, 443, 500, 561, 625, 692, 763, 838, 916, 997, 1082, 1170, 1262, 1357, 1456, 1558, 1664, 1773, 1886, 2002, 2121, 2244, 2371, 2501, 2634, 2771, 2911, 3055, 3202, 3353, 3507, 3665, 3826, 3990, 4158 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = A022838(A000290(n));

A171970(n)*A005843(n) <= a(n);

a(n) <= 4*A171971(n); 0 <= a(n) - 4*A171971(n) < 4.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Wikipedia, Tetrahedron

Eric Weisstein's World of Mathematics, Tetrahedron

FORMULA

a(n) = floor(n^2 * sqrt(3)).

PROG

(Haskell)

a171972 = floor . (* sqrt 3) . fromInteger . a000290

-- Reinhard Zumkeller, Dec 15 2012

CROSSREFS

Cf. A171974, A171973, A171975, A000290.

Sequence in context: A227952 A140091 A255605 * A225285 A165454 A063525

Adjacent sequences:  A171969 A171970 A171971 * A171973 A171974 A171975

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jan 20 2010

STATUS

approved

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Last modified August 21 13:32 EDT 2017. Contains 290890 sequences.