%N 1/4 of the even edge of least 2-adic valuation of a primitive 3-simplex (0, b=A031173, c=A031174, d=A031175).
%C Each primitive 3-simplex (0,b,c,d) with b > c > d is built by 1 odd edge and 2 even edges; the edge that is considered here is the even one with the least 2-adic valuation.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TrirectangularTetrahedron.html">Trirectangular Tetrahedron</a>
%Y Cf. A298044, A298047, A031173, A031174, A031175.
%A _Ralf Steiner_, Jan 11 2018