A right isosceles triangle has a hypotenuse that's √2 (1.41) and 1/√2 = 0.71.

Stack Overflow seems to think it's around 2.4x, but I am not sure I could ever follow the math and I certainly can't now. I think the amplitude makes the difference here and SO is answering a different question, otherwise this article would be wrong and that wasn't my impression the first time I encountered this topic.

second edit: The article linked from this article says:

So a crinkle wall with amplitude 1.4422 uses about as many bricks as a straight wall twice as thick.