Euler's partition theorem and the combinatorics of -sequences

Euler's partition theorem and the combinatorics of -sequences Euler's partition theorem and the combinatorics of -sequences

01.06.2015 Views

Let u l and v l be the roots of the polynomial x 2 − lx + 1: Then u l = l + √ l 2 − 4 ; v l = l − √ l 2 − 4 2 2 u l + v l = l; u l v l = 1. a (l) n = un l − v n l u l − v l . For real r, define ∆ (l) r = ul r + v l r . Then for integer n ∆ (l) n = a (l) n+1 − a(l) n−1 . (∆ is the l analog of “2”.) (∆ (l) n/2 )2 = u n l + 2(u lv l ) n/2 + v n l = ∆ (l) n + 2. ∆ (l) −r = u−r l + v −r l = vl r + ur l = ∆(l) r

A 3-term recurrence for the l-nomial [LS] ( n k ) (l) = ( n − 2 k ) (l) + ∆ (l) n−1 ( ) n − 2 (l) + k − 1 ( ) n − 2 (l) k − 2 Proof: Use identities: a (l) n+k − a(l) n−k = ∆(l) n a (l) k . a n (l) a (l) n−1 − a(l) k a(l) k−1 = a(l) n−k a(l) n+k−1 .

A 3-term recurrence for <strong>the</strong> l-nomial [LS]<br />

( n<br />

k<br />

) (l)<br />

=<br />

( n − 2<br />

k<br />

) (l)<br />

+ ∆ (l)<br />

n−1<br />

( ) n − 2 (l)<br />

+<br />

k − 1<br />

( ) n − 2 (l)<br />

k − 2<br />

Pro<strong>of</strong>: Use identities:<br />

a (l)<br />

n+k − a(l)<br />

n−k = ∆(l) n a (l)<br />

k .<br />

a n<br />

(l) a (l)<br />

n−1 − a(l) k<br />

a(l) k−1 = a(l) n−k a(l) n+k−1 .

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