A243304 Least number k > 0 such that 3^k contains at least an n-digit long substring of the infinite string "98765432109876543210987654...".
1, 5, 13, 50, 213, 536, 536, 536, 9354, 63202, 117150, 1314904, 2572181, 2572181
Offset: 1
Examples
3^5 = 243 contains a 2-digit substring of the infinite string "98765432109876543210987654..." (in this case, "43"). So a(2) = 5.
Crossrefs
Cf. A243295.
Programs
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Python
def Rev(n): rev = '' for i in str(n): rev = i + rev return rev def a(n): lst = [] for b in range(1,10**n): if len(str(3**b)) >= n: lst.append(b) break for k in range(lst[0],50000): for i in range(10): s = '' s += str(i) for j in range(i+1,i+n): dig = j%10 s+=str(dig) if str(3**k).find(Rev(s)) > -1: return k n = 1 while n < 100: print(a(n),end=', ') n += 1
Extensions
a(10)-a(12) from Hiroaki Yamanouchi, Sep 26 2014
a(13)-a(14) from Delbert L. Johnson, Apr 13 2024
Comments