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A181611 Position of rightmost zero in 2^n (including leading zero). 2
1, 1, 1, 2, 2, 2, 3, 3, 3, 2, 2, 2, 4, 5, 5, 5, 2, 6, 6, 5, 5, 1, 1, 8, 8, 4, 9, 9, 3, 8, 10, 10, 10, 11, 11, 11, 12, 4, 12, 11, 8, 1, 1, 5, 5, 12, 12, 3, 15, 7, 16, 3, 3, 7, 8, 8, 8, 12, 7, 7, 10, 1, 1, 7, 4, 4, 21, 13, 7, 4, 4, 22, 6, 6, 4, 23, 24, 13, 2, 4, 25, 1, 1, 11, 6, 26, 3, 2, 12, 12, 12, 11, 14, 14, 23, 3, 3, 4, 4, 4, 3, 1, 1, 2, 2, 2, 6, 6, 8, 2, 2, 2, 3, 3, 3, 17, 2, 5, 6, 6, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

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

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A215887(A000079(n)). - Michel Marcus, Jan 01 2016

EXAMPLE

2^10 = 1024, the rightmost zero is in position 2, so a(10) = 2. Another example, 2^5 = 32, so we need to add a leading zero: 032, thus the rightmost zero will be in position 2, and a(5) = 2.

MAPLE

A181611 := proc(n) local dgs, i ; dgs := convert(2^n, base, 10) ; i := ListTools[Search](0, dgs) ; if i > 0 then i-1; else nops(dgs) ; end if ; end proc: # R. J. Mathar, Jan 30 2011

a:= proc(n) local m, i;

      m:= 2^n;

      for i from 0 while m>0 and irem(m, 10, 'm')<>0

      do od; i

    end:

seq(a(n), n=1..121);  # Alois P. Heinz, Feb 05 2011

MATHEMATICA

Table[Position[Reverse[Prepend[IntegerDigits[2^n], 0]],

    0][[1]][[1]] - 1, {n, 121}]

PROG

(PARI) a(n) = {my(d = Vecrev(digits(2^n))); for (i=1, #d, if (!d[i], return (i-1)); ); #d; } \\ Michel Marcus, Jan 01 2016

CROSSREFS

Cf. A031142, A031141.

Cf. A000079, A215887.

Sequence in context: A177868 A178701 A117501 * A064740 A080967 A078570

Adjacent sequences:  A181608 A181609 A181610 * A181612 A181613 A181614

KEYWORD

nonn,base

AUTHOR

Tanya Khovanova, Jan 30 2011

STATUS

approved

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Last modified July 21 04:27 EDT 2017. Contains 289632 sequences.