4 Positive Integers in Arithmetic Sequence which have Same Euler Phi Value/Mistake
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Source Work
1986: David Wells: Curious and Interesting Numbers:
- The Dictionary
- $72$
1997: David Wells: Curious and Interesting Numbers (2nd ed.):
- The Dictionary
- $72$
Mistake
- $\map \phi {72} = \map \phi {78} = \map \phi {84} = \map \phi {90} = 24$. This is the smallest set of four numbers in arithmetical progression whose $\phi$ values are equal. The next two $4$-term arithmetical progressions with equal $\phi$ values start at $216$ and $76,236$ and each has a common difference, $6$.
Correction
The last one of those should say $76,326$.
Sources
- 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $72$
- 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $72$