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Fermat knew that a fourth power cannot be the sum of two other fourth powers (the n = 4 case of Fermat's Last Theorem; see Fermat's right triangle theorem). Euler conjectured that a fourth power cannot be written as the sum of three fourth powers, but 200 years later, in 1986, this was disproven by Elkies with: 20615673 4 = 18796760 4 ...
The Pennsylvania Railroad kept producing 0-4-0 classes long after all other major railroads had abandoned development of the type, building their final A5s class into the 1920s. The A5s was a monster among 0-4-0s, larger than many 0-6-0 designs, with modern features found on few others of its type, such as superheating, power reverse, and ...
Under the Whyte notation for the classification of steam locomotives, 0-4-4 represents the wheel arrangement of no leading wheels, four powered and coupled driving wheels on two axles, and four trailing wheels on two axles. This type was only used for tank locomotives. In the UK 0-4-4 tanks were mainly used for suburban or rural passenger duties.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the 0-4-0+0-4-0 is an articulated locomotive of the Garratt type. The wheel arrangement is effectively two 0-4-0 locomotives operating back-to-back or face-to-face, with the boiler and cab suspended between the two power units.
Four fours is a mathematical puzzle, the goal of which is to find the simplest mathematical expression for every whole number from 0 to some maximum, using only common mathematical symbols and the digit four.
The 0-4-0+4 wheel arrangement was usually found on railmotors, vehicles for passenger carrying that operated on routes where passenger numbers were light.It usually consisted of a single coach with its own prime mover.
Coupled with an elegant French style tender, the second batch of the 240P class was aesthetically much more pleasing. With a power output of 4,700 horsepower (3,500 kilowatts), the 240P class was reputed to have the highest power-to-weight ratio of any steam locomotive. Discussion continues as to how robust they were mechanically, for example ...
Five years after new locomotive construction had begun at the West Point Foundry in the United States with the 0-4-0 Best Friend of Charleston in 1831, the first 4-4-0 locomotive was designed by Henry R. Campbell, at the time the chief engineer for the Philadelphia, Germantown and Norristown Railway.