sesquiplicate

Surface form sesqui- (“one and a half”) +‎ plicate (“fold”); by analogy with duplicate.

sesquiplicate (not comparable)

1. Magnified by one and one-half; in a ratio of three to two.

• sesquialteral, sesquialterate: sesquialteral ratio = ratio of 3 to 2
• sesquiplicate proportion
• sesquiplicate ratio
• subsesquiplicate: subsesquiplicate ratio = 2/3rd power of the ratio

• duplicate – two times
• triplicate – three times

• half again

1729: And all astronomers agree that their periodic orbits are in the sesquiplicate proportion of the semi-diameters of their orbits; and so it manifestly appears from the following table. — Andrew Motte, translating Isaac Newton's Philosophiae Naturalis Principia Mathematica

Note: "in the sesquiplicate proportion" (ratio) means increasing as the square root of the cube, that is, as x^3/2, just as "in the duplicate ratio" would mean increasing as the square.