

A030000


a(n) = smallest nonnegative number k such that the decimal expansion of 2^k contains the string n.


21



10, 0, 1, 5, 2, 8, 4, 15, 3, 12, 10, 40, 7, 17, 18, 21, 4, 27, 30, 13, 11, 18, 43, 41, 10, 8, 18, 15, 7, 32, 22, 17, 5, 25, 27, 25, 16, 30, 14, 42, 12, 22, 19, 22, 18, 28, 42, 31, 11, 32, 52, 9, 19, 16, 25, 16, 8, 20, 33, 33, 23, 58, 18, 14, 6, 16, 46, 24, 15, 34, 29, 21, 17, 30
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OFFSET

0,1


LINKS

Giovanni Resta, Table of n, a(n) for n = 0..10000 (terms up to a(1000) from T. D. Noe)


EXAMPLE

2^12 = 4096 is first power of 2 containing a 9, so a(9) = 12.


MATHEMATICA

Table[ i=0; While[ StringPosition[ ToString[ 2^i ], ToString[ n ] ]=={}, i++ ]; i, {n, 0, 80} ]


PROG

(Haskell)
import Data.List (isInfixOf, findIndex)
import Data.Maybe (fromJust)
a030000 n =
fromJust $ findIndex (show n `isInfixOf`) $ map show a000079_list
 Reinhard Zumkeller, Aug 04 2011


CROSSREFS

Cf. A030001 (the actual powers of 2), A063565, A018856, A000079.
See also A321043.
Sequence in context: A288123 A261334 A038689 * A221809 A291451 A323836
Adjacent sequences: A029997 A029998 A029999 * A030001 A030002 A030003


KEYWORD

nonn,base


AUTHOR

N. J. A. Sloane.


EXTENSIONS

More terms from Hans Havermann


STATUS

approved



