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A023415 If any power of 2 ends with k 8's and 9's, they must be the first k terms of this sequence in reverse order.

%I A023415 #42 Jul 22 2024 00:58:36
%S A023415 8,8,8,9,8,9,9,8,9,8,9,8,8,9,9,8,9,8,9,9,9,8,8,8,8,9,8,8,8,8,9,9,9,9,
%T A023415 8,9,8,8,9,9,8,8,9,9,8,9,8,8,9,8,9,8,9,8,8,8,8,8,8,9,9,9,9,8,9,8,8,8,
%U A023415 9,9,8,8,9,8,8,9,9,8,8,9,9,9,8,9,9,9,9,9,9,8,8,9,8,8,9,9,9,9,9,9,8,8,8,9,9,8,8,8
%N A023415 If any power of 2 ends with k 8's and 9's, they must be the first k terms of this sequence in reverse order.
%C A023415 Upper limit of backward value of 2^n and n!. - _Simon Plouffe_, Mar 23 2009
%H A023415 Ray Chandler, <a href="/A023415/b023415.txt">Table of n, a(n) for n = 1..10000</a>
%o A023415 (Python)
%o A023415 # upper limit of backward value of 2^n
%o A023415 a,i=8,0; x=a
%o A023415 while i < 200:
%o A023415      i+=1; print(x, end=',')
%o A023415      if a%2**(i+1) == 0: x=8
%o A023415      else: x=9
%o A023415      a+=x*10**i
%o A023415 # _Cezary Glowacz_, Mar 11 2017
%Y A023415 Cf. A145679.
%K A023415 nonn,base
%O A023415 1,1
%A A023415 _David W. Wilson_