Lisa calls a natural number obedient if she can be written as a product of the two figures following on each other. Example: The number 20 is obedient, because 20 = 4∙5.

Points: To every obedient number there is at least one second obedient number which proves an obedient number with the first one multiplied again.

Example: 2∙3=6 and 3∙4=12 and 6∙12=72 which is: 8∙9

Is the sentence true??Why?? Is there a proof?

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