# Le Monde puzzle [#1063]

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A simple (summertime?!) arithmetic Le Monde mathematical puzzle

1. A “powerful integer” is such that all its prime divisors are at least with multiplicity 2. Are there two powerful integers in a row, i.e. such that both n and n+1 are powerful?
2.  Are there odd integers n such that n⊃2; – 1 is a powerful integer ?

The first question can be solved by brute force.  Here is a R code that leads to the solution:

```isperfz <- function(n){
divz=primeFactors(n)
facz=unique(divz)
ordz=rep(0,length(facz))
for (i in 1:length(facz))
ordz[i]=sum(divz==facz[i])
return(min(ordz)>1)}

lesperf=NULL
for (t in 4:1e5)
if (isperfz(t)) lesperf=c(lesperf,t)
twinz=lesperf[diff(lesperf)==1]
```

with solutions 8, 288, 675, 9800, 12167.

The second puzzle means rerunning the code only on integers n⊃2;-1…

```[1] 8
[1] 288
[1] 675
[1] 9800
[1] 235224
[1] 332928
[1] 1825200
[1] 11309768
```

except that I cannot exceed n⊃2;=10⁸. (The Le Monde puzzles will now stop for a month, just like about everything in France!, and then a new challenge will take place. Stay tuned.)

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