a_k=\cases{(0.\underbrace{20101...0101}_{k+2~cifre})^{a_{k-1}},& \mbox{ako je} k \mbox{neparno}\cr (0.\underbrace{20101...01011}_{k+2~cifre})^{a_{k-1}},& \mbox{ako je} k \mbox{parno}}