Serials jumping

I have a serial column on a test box DB. I'm
using "select nextval('some_seq') as id" to insert a
id in sequence. It doesn't return the next value but
at least 4 or so (random) ahead of the current
value. Is this to be expected?

Is this the most efficient way to retreive an id value
for insert a row then insert the resulting row into
the related tables?

Is there a more efficient/proper way? I would like all
my records to increment by 1 if possible. I'd be very
grateful to read your opinion.

Thank you.

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