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Position of rightmost digit 0 in 2^A031140(n).
5

%I #31 Oct 11 2019 16:54:48

%S 2,5,8,11,12,13,14,23,36,38,54,57,59,93,115,119,120,121,136,138,164,

%T 174,176,191,196,212,217,227,233,249

%N Position of rightmost digit 0 in 2^A031140(n).

%C "Positions" are counted 0,1,2,3,... starting with the least significant digit.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Zero.html">Zero.</a>

%t best = 0;

%t x = Select[Range[10000],

%t If[(t = First@

%t First@StringPosition[StringReverse@ToString@(2^#), "0"]) >

%t best, best = t; True] &] ;

%t First /@ First /@

%t StringPosition[StringReverse[ToString /@ (2^x)],

%t "0"] - 1 (* _Robert Price_, Oct 11 2019 *)

%o (PARI) m=0;for(k=0,oo,d=digits(2^k);for(j=0,#d-1,d[#d-j]||(j>m&&print1(m=j,",")||break))) \\ _M. F. Hasler_, Jun 21 2018

%Y Cf. A031140, A031142, A031143.

%K nonn,base,more

%O 1,1

%A _Matthew Cook_, _Dan Hoey_, _Eric W. Weisstein_, _David W. Wilson_

%E More terms from _Dan Hoey_