>>33
 Sn=1*2^0+3*2^1+5*2^2+・・・+(2n-1)*2^(n-1)
-)2Sn=    1*2^1+3*2^2+5*2^3+・・・+(2n-3)*2^(n-1)+(2n-1)*2^(n)
-Sn=2{3^0+3^1+3^2+3^3+・・・+3^(n-1)}+(2n-1)*2^(n)