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2004 | OriginalPaper | Buchkapitel

Identities versus bijections

verfasst von : Martin Aigner, Günter M. Ziegler

Erschienen in: Proofs from THE BOOK

Verlag: Springer Berlin Heidelberg

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Consider the infinite product (1 + x)(1 + x2)(1+ x3)(1+ x4) … and expand it in the usual way into a series $$\sum {_{n \geqslant 0}{a_n}{x^n}} $$ by grouping together those products that yield the same power xn. By inspection we find for the first terms (1)$$\prod\limits_{k \geqslant 1} {\left( {1 + {x^k}} \right) = 1 + x + {x^2} + 2{x^3} + 2{x^4} + 3{x^5} + 4{x^6} + 5{x^7} + ....} $$ So we have e. g. a6 = 4 a7 = 5, and we (rightfully) suspect that a n goes to infinity with n→ ∞.

Metadaten
Titel
Identities versus bijections
verfasst von
Martin Aigner
Günter M. Ziegler
Copyright-Jahr
2004
Verlag
Springer Berlin Heidelberg
DOI
https://doi.org/10.1007/978-3-662-05412-3_29

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