A181611 Position of rightmost zero in 2^n (including leading zero).

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

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: A071451 A177868 A178701 * A064740 A080967 A078570

Adjacent sequences: A181608 A181609 A181610 * A181612 A181613 A181614

Keyword

nonn,base

Author

Tanya Khovanova, Jan 30 2011

Status

approved