#define PIXEL_COUNT 60
A Nano can supply a maximum of ~50mA from it's 5volt pin when powered from 12volt on V-in (raw).
That's a maximum of ONE neopixel.
If you power the Nano from USB, then the 5volt limitation is ~450mA,
and the Nano can power up to eight Neopixels.
For 60 Neopixels, you need a 5volt/3.5Amp supply.
The Nano can be powered from that as well (on the 5volt pin).
Leo..