Frequency spectrum for EPIC 249630037 after prewhitening with the first overtone and its harmonics. The positions of the first overtone and its harmonics are marked with red dashed lines. The blue dashed line corresponds to the location of the f_0.68 signal (which was not detected in this star). With a blue region, we marked the frequency range of the f_0.61 signal, and with an orange region, we marked the corresponding frequency range of the subharmonic. With a blue arrow, we marked the signal that forms a period ratio that fits the RRd sequence.