Problems & Puzzles: Puzzles

 

 

Problems & Puzzles: Puzzles

Puzzle 1243 Consecutive Cube root smooth numbers

Giorgos Kalogeropouls sent the following nice puzzle:

Cube Root Smooth (CRS) numbers are numbers k whose largest prime factor lpf(k) <= k^(1/3) (A090081)
In this challenge you are asked to find the least number k that produces a run of exactly n consecutive CRS numbers.

n=1 -> 8
n=2 -> 2400, 2401
n=3 -> 134848, 134849, 134850
n=4 -> 3678723,  3678724, 3678725, 3678726

Example:

n=2
  • 2400 = 25 × 3 × 52 & 5^3 = 125< 2400
  • 2401 = 74 & 7^3 = 343 < 2401
Q1: Find the least k that starts a run of 5,6,7... consecutive CRS numbers.
Q2: Is this sequence infinite?
Q3: What is the longest run of consecutive CRS numbers that you can find?

   


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