experimental-projects/oeis-research/Hans Havermann/Least k such that the decimal representation of 2^k contains all possible n-digit strings/prog.sf

#!/usr/bin/ruby

# Least k such that the decimal representation of 2^k contains all possible n-digit strings
# https://oeis.org/A360656

# Known terms:
#   68, 975, 16963, 239697, 2994863

func a(n, from=0) {

    var v = gather {
        @(0..9).variations_with_repetition(n, {|*a|
            take(a.join)
        })
    }

    for k in (from..Inf) {
        var t = (2**k -> to_s)
        if (v.all { t.contains(_) }) {
            return k
        }
    }
}

for n in (1..100) {
    say "a(#{n}) = #{a(n)}"
}

__END__
a(1) = 68
a(2) = 975
a(3) = 16963