

A031140


Position of rightmost 0 in 2^n increases.


4



10, 20, 30, 40, 46, 68, 93, 95, 129, 176, 229, 700, 1757, 1958, 7931, 57356, 269518, 411658, 675531, 749254, 4400728, 18894561, 33250486, 58903708, 297751737, 325226398, 781717865, 18504580518, 27893737353, 103233492954
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OFFSET

1,1


COMMENTS

"Positions" are counted 0,1,2,3,... starting with the least significant digit.
I.e., look for increasing number of nonzero digits after the rightmost digit '0'.  M. F. Hasler, Jun 21 2018


LINKS

Table of n, a(n) for n=1..30.
Eric Weisstein's World of Mathematics, Zero.


EXAMPLE

From M. F. Hasler, Jun 21 2018: (Start)
2^10 = 1024 is the first power of 2 to have a digit '0', which is the third digit from the right, i.e., it has to its right no digit '0' and two nonzero digits.
2^20 = 1048576 is the next larger power with a digit '0' having to its right no digit '0' and more (namely 5) nonzero digits than the above 1024.
After 2^46 = 70368744177664 there is 2^52 = 4503599627370496 having a '0' further to the left, but this digit has another '0' to its right and therefore cannot be considered: The next term having more nonzero digits after its rightmost '0' is only 2^68. (End)


MATHEMATICA

best = 0;
Select[Range[10000],
If[(t = First@
First@StringPosition[StringReverse@ToString@(2^#), "0"]) >
best, best = t; True] &] (* Robert Price, Oct 11 2019 *)


PROG

(PARI) m=0; for(k=0, oo, d=digits(2^k); for(j=0, #d1, d[#dj](j>m&&(m=j)&&print1(k", ")break))) \\ M. F. Hasler, Jun 21 2018


CROSSREFS

Cf. A031141, A031142, A031143.
Sequence in context: A069534 A237416 A236507 * A095973 A299970 A037997
Adjacent sequences: A031137 A031138 A031139 * A031141 A031142 A031143


KEYWORD

nonn,base,changed


AUTHOR

Matthew Cook, Dan Hoey, Eric W. Weisstein, David W. Wilson


EXTENSIONS

More terms from Dan Hoey.


STATUS

approved



