An Unusual Identity from Ramanujan's Notebooks

In this paper, we examine a unique identity—Entry 27 from Ramanujan’s Notebook IV. By leveraging the symmetry properties of integral quadratic forms, we provide natural representations of both sides of the identity in terms of three distinct classes of binary quadratic forms with discriminant −252. The combination of integral quadratic forms and exact covering systems leads to a collection of surprisingly elegant identities.

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Publication Details

Journal
International Journal of Number Theory
Published
2026-04-21
DOI
https://doi.org/10.1142/s1793042126500843
Primary Topic
Advanced Mathematical Identities
Type
article
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article

An Unusual Identity from Ramanujan's Notebooks

Zhu Cao
International Journal of Number Theory
Advanced Mathematical Identities
article

An Unusual Identity from Ramanujan's Notebooks

Zhu Cao
article en

Abstract

In this paper, we examine a unique identity—Entry 27 from Ramanujan’s Notebook IV. By leveraging the symmetry properties of integral quadratic forms, we provide natural representations of both sides of the identity in terms of three distinct classes of binary quadratic forms with discriminant −252. The combination of integral quadratic forms and exact covering systems leads to a collection of surprisingly elegant identities.

International Journal of Number Theory
Twitter (United States) (US)
Reduced inequalities
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Advanced Mathematical Identities
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An Unusual Identity from Ramanujan's Notebooks — Zhu Cao · International Journal of Number Theory (2026) | TGRS Research Map | TGRS