To obtain the sum of successive odd digits:      ex.  1+3+5+7+9+11=36

-To obtain the sum of successive odd digits, count the number of odd digits and square this number.     ex.  1+3+5+7+9+11 has 6 digits, and squaring this yields the answer.  6×6=36

This is easy:      1+3=4       1+3+5=9       1+3+5+7=16      1+3+5+7+9=25