cp's OEIS Frontend

A238508 Smallest number m such that 3^m contains a string of n consecutive decreasing integers in its decimal representation.

%I A238508 #11 May 22 2025 10:21:37
%S A238508 0,5,13,50,213,536,536,4582,63202,163984
%N A238508 Smallest number m such that 3^m contains a string of n consecutive decreasing integers in its decimal representation.
%e A238508 5 is the smallest exponent such that 3^5 contains two consecutive decreasing integers (3^5 = 243).
%e A238508 13 is the smallest exponent such that 3^13 contains three consecutive decreasing integers (3^13 = 1594323).
%o A238508 (Python)
%o A238508 def StrDec(x):
%o A238508   for n in range(10**5):
%o A238508     count = 0
%o A238508     i = 0
%o A238508     string = str(3**n)
%o A238508     if len(string) == x and x == 1:
%o A238508       return n
%o A238508     while i < len(string)-1:
%o A238508       if int(string[i]) == int(string[i+1])-1:
%o A238508         count += 1
%o A238508         i += 1
%o A238508       else:
%o A238508         if count >= x-1:
%o A238508           return n
%o A238508         else:
%o A238508           count = 0
%o A238508           i += 1
%o A238508     if count >= x-1:
%o A238508       return n
%o A238508 x = 1
%o A238508 while x < 15:
%o A238508   print(StrDec(x))
%o A238508   x += 1
%Y A238508 Cf. A238449, A215727.
%K A238508 nonn,base,fini,full
%O A238508 1,2
%A A238508 _Derek Orr_, Feb 27 2014
%E A238508 a(9)-a(10) from _Giovanni Resta_, Mar 02 2014