Problem 61015. find the nth number (plus)

  • Created by Le
this problem is the harder version of Problem 61014.
The numbers 2 and 7 are called lucky numbers, an integer containing only the digits 2 and 7 is also called lucky number. The problem is, given a sequence of lucky numbers arranged in the following order:
Lucky_num=[ 2, 7, 22, 27, 72, 77, 222, 227, 272, 277, 722, 727, 772, 777,.......]
Write a function that takes n as a parameter, we expect the output to be the nth lucky number
Eg:
n=8
-> output: 227
note: with this plus version you have to find the Nth number with extremely large N, for example 1e9, return n in string form
n=1e9
->ouput: "77277722772727722722777777272"
Solve

Solution Stats

100.0% Correct | 0.0% Incorrect
Last Solution submitted on Oct 21, 2025

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