Loreen – Tattoo, synth sound intro? – Sound Design Forum

The “hollow, plastic tube-like” sound is probably done using a comb filter and a multiband compressor to emphasize the midrange and making that character louder.
It seems quite difficult to get exactly same sound. I got somewhat similar sound in Serum using
Unison saw -> Cmb HL6+ comb filter -> MG Low 18 filter -> Multiband compressor.
And plucky envelopes modulating volume and the filters.

The exponential rhythms can be done quite easily by automating arpeggiator rate, or by drawing the MIDI notes. You could do it also using LFO inside the synth, like tehlord was suggesting. There are many Youtube videos explaining alternative ways to do it.