function p68( t ) {
	return 0.27369129607732343398e0 + (0.51793846023052643767e-2 + (0.53350152258326602629e-4 + (0.45379208848865015485e-6 + (0.31874057245814381257e-8 + (0.18277905010245111046e-10 + 0.83144182364444444445e-13 * t) * t) * t) * t) * t) * t;
}
Chebyshev polynomial for \[0.68, 0.69).

@private
@param {number} t - scaled value
@returns {number} result