There are actually B, C and D formats with the same properties, just scaled up or down slightly if you need something in between, for example B4 is basically A3.5, C4 is A3.75 and D4 is A4.25 if you plug it into the power-of-2 formula. (Later, C and D were removed because very few people used the quarter-steps.)
There are actually B, C and D formats with the same properties, just scaled up or down slightly if you need something in between, for example B4 is basically A3.5, C4 is A3.75 and D4 is A4.25 if you plug it into the power-of-2 formula. (Later, C and D were removed because very few people used the quarter-steps.)