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Concrete mathematics : a foundation for computer science

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A ANSWERS TO EXERCISES 545<br />

Subtract zbm/( 1 - z”m ) from both sides and set z = e2xi/am. The left side is<br />

infinite, and the right side will be finite unless a,,-1 = a,.<br />

7.33 (-l)n--m+‘[n>m]/(n - m).<br />

7.34 We can also write G,(z) = tk,+,m+,,k,+,=n (kl~~k+~+l)(zm)km+l. In<br />

general, if<br />

we have G, = z1 G,_., + z2GnP2 +. . . + zrGnmmr + [n=O], and the generating<br />

function is l/( 1 - z1 w - zzw2 - . . . - z,.w’). In the stated special case the<br />

answer is l/(1 -w - zmwm+‘). (See (5.74) <strong>for</strong> the case m = 1.)<br />

7’35 Cal t t0

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