Pinning is in the Shared Pool in the SGA. So it is local to an instance.
Therefore, you would need to execute it in each instance (i.e. on each node).
Note : However, with sequences in RAC, you have to be careful with the definition. Have you defined it or do you need to define it as CACHE/NOCACHE ? Have you defined it or do you need to define it as ORDER (to guarantee order generation in RAC) ?
Hemant K Chitale