You Are Asked to Design a New Set of Coins

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You are asked to design a new set of coins. All coins will be circular and colored silver, but of different diameters

Researchers have found that an ideal coin system meets the following requirements:
Diameters of coins should not be smaller than 15 mm and not be larger than 45 mm.
Given a coin, the diameter of the next coin must be at least 30% larger.
The minting machinery can only produce coins with diameters of a whole number of millimeters (e.g., 17 mm is allowed, but 17.3 mm is not.). You are asked to design a set of coins that satisfy the above requirements. You should start with a 15-mm coin, and your set should contain as any coins as possible. What would be the diameters of the coins in your set?