A171975 Integer part of the circumsphere radius of a regular tetrahedron with edge length n.

0, 1, 1, 2, 3, 3, 4, 4, 5, 6, 6, 7, 7, 8, 9, 9, 10, 11, 11, 12, 12, 13, 14, 14, 15, 15, 16, 17, 17, 18, 18, 19, 20, 20, 21, 22, 22, 23, 23, 24, 25, 25, 26, 26, 27, 28, 28, 29, 30, 30, 31, 31, 32, 33, 33, 34, 34, 35, 36, 36, 37, 37, 38, 39, 39, 40, 41, 41, 42, 42, 43, 44, 44, 45, 45

Offset: 1

Author

Reinhard Zumkeller, Jan 20 2010

Keywords

• nonn

Comments

-3 <= 4*a(n) - 3*A171974(n) < 3;

a(n)*A171974(n) <= A007590(n).

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Tetrahedron
• Wikipedia, Tetrahedron

Crossrefs

Cf. A171973, A171972, A022840. Beatty sequence of A187110.

Programs

Haskell

a171975 = floor . (/ 4) . (* sqrt 6) . fromInteger
-- Reinhard Zumkeller, Dec 15 2012

Formula

a(n) = floor(n*sqrt(6)/4).