Competition problem — Number theory

Library / /14 of 520

Number theory Difficulty 5.2 AIME, harder Find the answer

12. Find $\phi(n)$ for the integers $n$ with $13 \leqslant n \leqslant 20$ .

Your answer

A number or a short expression. Spacing and $ signs are ignored.

Solution

12. $\phi(13)=12, \phi(14)=6, \phi(16)=8, \phi(17)=16, \phi(18)=6, \phi(19)=18, \phi(20)=8$

Want a route through all this instead of an archive? The track puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.