sicp-ex-3.66

(1, 100) : 198
(100, 100): 99*2^200 - 1 + 2^99. 
the equation for (m, n) is: 
n = 1:   2^m - 1;
n = 2:   2^m - 1 + 2^(m-1);
n > 2:   2^m - 1 + 2^(m+1) + (n-2)*2^m