A124908 a(n) = least integer j >= 0 such that n = floor((2^j)/(5^k)) for some integer k >= 0.

0, 1, 4, 2, 7, 5, 33, 3, 38, 8, 36, 6, 13, 34, 55, 4, 25, 39, 60, 9, 23, 37, 44, 58, 7, 14, 28, 35, 49, 56, 70, 5, 19, 26, 33, 40, 54, 61, 68, 10, 17, 24, 31, 103, 38, 45, 52, 59, 66, 73, 8, 15, 22, 29, 101, 36, 43, 115, 50, 57, 64, 136, 71, 6, 13, 85, 20, 27, 99, 34, 106, 41, 48

Offset

1,3

Comments

The k-sequence is A124916.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(2^j) = j. - Robert Israel, Jul 05 2018

Example

1 = floor(2^0/5^0), 2 = floor(2^1/5^0), 3 = floor(2^4/5^1), 4 = floor(2^2/5^0), ...,
so j-sequence = (0,1,4,2,...); k-sequence = (0,0,1,0,...).

Maple

f:= proc(n) local k;
if n = 2^ilog2(n) then return ilog2(n) fi;
for k from 1 do if ilog2(n*5^k) <> ilog2((n+1)*5^k) then return ilog2((n+1)*5^k) fi od
end proc:
map(f, [$1..100]); # Robert Israel, Jul 05 2018

Crossrefs

Cf. A124916.

Sequence in context: A271479 A259927 A002560 * A260593 A143370 A367832

Adjacent sequences: A124905 A124906 A124907 * A124909 A124910 A124911

Keyword

nonn,look

Author

Clark Kimberling, Nov 12 2006

Status

approved