On an identity of Ramanujan

International audience Proofs published so far in articles and books, of the Ramanujan identity presented in this note, which depend on Euler products, are essentially the same as Ramanujan's original proof. In contrast, the proof given here is short and independent of the use of Euler products.

Bottom Schur Functions

We give a basis for the space spanned by the sum $\hat{s}_\lambda$ of the lowest degree terms in the expansion of the Schur symmetric functions $s_\lambda$ in terms of the power sum symmetric functions $p_\mu$, where deg$(p_i)=1$. These lowest degree terms correspond to minimal border strip tableaux of $\lambda$. The dimension of the space spanned by $\hat{s}_\lambda$, where $\lambda$ is a partition of $n$, is equal to the number of partitions of $n$ into parts differing by at least 2. Applying the Rogers-Ramanujan identity, the generating function also counts the number of partitions of $n$ into parts $5k+1$ and $5k-1$. We also show that a symmetric function closely related to $\hat{s}_\lambda$ has the same coefficients when expanded in terms of power sums or augmented monomial symmetric functions.

Short and Easy Computer Proofs of the Rogers-Ramanujan Identities and of Identities of Similar Type

New short and easy computer proofs of finite versions of the Rogers-Ramanujan identities and of similar type are given. These include a very short proof of the first Rogers-Ramanujan identity that was missed by computers, and a new proof of the well-known quintuple product identity by creative telescoping.