Setup:
Brand new Pi3B+, New, confirmed good 2.5a USB power supply, HDMI monitor connected, USB keyboard and mouse connected. 8 & 16GB SD cards loaded with Raspbian Stretch & Lite (both 4/2018 versions). 3 different USB 64GB memory sticks (different manufacturers). SD and USB sticks tested on older Pi3Bs, known good working.
Pi3B+ set to boot from either SD or USB.When powered on and connected to HDMI monitor, I do not get lightning bolt indicating low power, and I do not get low voltage detected on command line.
After booting, and it does boot up to desktop or command line as appropriate using all the above.
My concern / issue is the green activity LED blinks 4 times rapidly, pauses 1 second, and repeats, continuously. Everything I googled relates to a no boot condition.
Is this something to be concerned about?
Thanks.