1,4

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

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

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

Wikipedia, Tetrahedron

Eric Weisstein's World of Mathematics, Tetrahedron

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

(Haskell)

a171975 = floor . (/ 4) . (* sqrt 6) . fromInteger

-- Reinhard Zumkeller, Dec 15 2012

Cf. A171973, A171972, A022840.

Sequence in context: A244229 A317596 A057355 * A160511 A079952 A055930

Adjacent sequences: A171972 A171973 A171974 * A171976 A171977 A171978

nonn

Reinhard Zumkeller, Jan 20 2010

approved