Die Formeln aus dem Link:
2y*30 + 2y-1*31 +2y-2*32 +.......+ 21*3y-1
= 2y + 2y*3/2 +2^y*32/2^2 +.......+ 2^y *3y-1 / 2^{y^1}
= 2y + 2^y * 3/2 +2^y * (3/2)^2 +.......+ 2^y* (3 / 2) ^{y-1} )
q = 3/2 = 1.5 = 3*2-1 , ao = 2^y, n = y-1 . Nun Formel von oben benutzen
2y*30 + 2y-1*31 +2y-2*32 +.......+ 21*3y-1
= 2^y * ( 1 - 1.5^{y-1+1}) / ( 1 - 1.5)
= 2^y * ( 1 - 1.5^{y}) / ( -0.5)
= 2^y * (1.5^y - 1) / 0.5
= 2^{y+1} (1.5^y - 1)
Bitte selber nachrechnen.