Sankaranarayanan and Sengupta introduced the function μ*(n) corresponding to the Möbius function. This is defined by the coefficients of the Dirichlet series 1/L f (s), where L f (s) denotes the L-function attached to an even Maaß cusp form f . We will examine partial sums of μ*(n). The main result is ∑n≤x μ*(n) = O(x exp(-Avlog x)), where A is a positive constant. It seems to be the corresponding prime number theorem. © Indian Academy of Sciences.