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%I #12 Jul 19 2020 02:16:54
%S 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,
%T 17,18,18,19,20,20,21,22,22,23,23,24,25,25,26,26,27,28,28,29,30,30,31,
%U 31,32,33,33,34,34,35,36,36,37,37,38,39,39,40,41,41,42,42,43,44,44,45,45
%N Integer part of the circumsphere radius of a regular tetrahedron with edge length n.
%C -3 <= 4*a(n) - 3*A171974(n) < 3;
%C a(n)*A171974(n) <= A007590(n).
%H Reinhard Zumkeller, <a href="/A171975/b171975.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Tetrahedron.html">Tetrahedron</a>
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Tetrahedron">Tetrahedron</a>
%F a(n) = floor(n*sqrt(6)/4).
%o (Haskell)
%o a171975 = floor . (/ 4) . (* sqrt 6) . fromInteger
%o -- _Reinhard Zumkeller_, Dec 15 2012
%Y Cf. A171973, A171972, A022840. Beatty sequence of A187110.
%K nonn
%O 1,4
%A _Reinhard Zumkeller_, Jan 20 2010
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