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An Identity Motivated by an Amazing Identity of Ramanujan

Number Theory 2019-01-16 v1

Abstract

Ramanujan stated an identity to the effect that if three sequences {an}\{a_n\}, {bn}\{b_n\} and {cn}\{c_n\} are defined by r1(x)=:n=0anxnr_1(x)=:\sum_{n=0}^{\infty}a_nx^n, r2(x)=:n=0bnxnr_2(x)=:\sum_{n=0}^{\infty}b_nx^n and r3(x)=:n=0cnxnr_3(x)=:\sum_{n=0}^{\infty}c_nx^n (here each ri(x)r_i(x) is a certain rational function in xx), then an3+bn3cn3=(1)n,n0. a_n^3+b_n^3-c_n^3=(-1)^n, \hspace{25pt} \forall \,n \geq 0. Motivated by this amazing identity, we state and prove a more general identity involving eleven sequences, the new identity being "more general" in the sense that equality holds not just for the power 3 (as in Ramanujan's identity), but for each power jj, 1j51\leq j \leq 5.

Keywords

Cite

@article{arxiv.1901.04842,
  title  = {An Identity Motivated by an Amazing Identity of Ramanujan},
  author = {James Mc Laughlin},
  journal= {arXiv preprint arXiv:1901.04842},
  year   = {2019}
}

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5 pages