Aug. 15th, 2020
This challenge was split into two parts: the first generated a number that represented the flag as a sum of combinations. The second part used the number generated from part one and encoded it into a ternary string, whos 1s and 2s each represented either the operation 2(x-1) or 2(x+1). In addition, each digit also multiplied the number by two.
import numpy as np import scipy.misc as sc enc = 5550332817876280162274999855997378479609235817133438293571677699650886802393479724923012712512679874728166741238894341948016359931375508700911359897203801700186950730629587624939700035031277025534500760060328480444149259318830785583493 def pt1(num): copy = (np.base_repr(num,base=3)) r = 1 for i in range(1,len(copy)): a = int(copy[i]) r*=2 if a==1: r+=1 elif a==2: r-=1 return r def pt2(num): n,k,r = -1,0,0 for i,c in enumerate(bin(num)[:2:-1]): n+=1 if c=='1': k+=1 r+=sc.comb(n,k, exact=1) return r print(bytes.fromhex(hex(pt2(pt1(enc)))[2:]).decode('utf-8'))