Name Hideo Takioka Osaka City University Session Jan 10 16:20~16:40 E11-103 The zeroth coefficient polynomial of a $(2,1)$-cable knot The zeroth coefficient polynomial is the constant term of the HOMFLYPT polynomial with respect to one of the two variables. We show several calculation results for the zeroth coefficient polynomials of $(2,1)$-cable knots. In particular, we give examples of infinitely many knots with the same HOMFLYPT polynomials, which can be distinguished by the zeroth coefficient polynomials of their $(2,1)$-cable knots. 103-1-10/Takioka.pdf