1, 4, 1, 5 ...

This series counts the chimes of a grandfather clock. On the hour, the clock rings out a number of chimes equal to the hour. On the half-hour, it always chimes once. I'll list the times with their associated chimes below:

12:00 - 12 chimes
12:30 - 1 chime
1:00 - 1 chime
1:30 - 1 chime
2:00 - 2 chimes
2:30 - 1 chime
3:00 - 3 chimes
3:30 - 1 chime
4:00 - 4 chimes
4:30 - 1 chime
5:00 - 5 chimes