User blog comment:Deedlit11/Bignum Bakeoff appetizer/@comment-5529393-20140922175020/@comment-2033667-20140923043622

100 characters.

i = 9 << 99999, b = 3; B(x,y) {return y && y % b * pow(b+1, B(0,x)) + B(x+1, y/b);} main {while(i = B(0,i)-1) b++; return b;}