Inserting all defaults

Is it possible to do an insert with no values?

e.g.

CREATE TABLE a (num INTEGER DEFAULT 1);
INSERT INTO a; or INSERT INTO a VALUES ();

I'd like to do this when a database is first created to insert the default
set of values that I have for every table e.g. a default system
configuration.

This might appear more useful like so:

CREATE TABLE config (
config_code SERIAL PRIMARY KEY,
parameter_1 INTEGER DEFAULT 999,
parameter_2 INTEGER DEFAULT 2000
);

INSERT INTO config;

CREATE TABLE device (
device_code SERIAL PRIMARY KEY,
config_code INTEGER REFERENCES config DEFAULT 1 NOT NULL,
);

Thanks,

R.