A $q$-multinomial expansion of LLT coefficients and plethysm   multiplicities
  Lascoux, Leclerc and Thibon\cite{LLT} introduced a family of symmetric polynomials, called LLT polynomials. We prove a $q$-multinomial expansion of the coefficients of LLT polynomials in the case where $ \boldsymbol{\mu} = \underbrace{(\mu,...,\mu)}_{n}$ and define a $q$-analog of a sum of the plethysm multiplicities. 
Kazuto Iijima
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