how to increase the radius to find the player?

 

I Add:

protected void applyEntityAttributes()
    {
        super.applyEntityAttributes();
        this.getEntityAttribute(SharedMonsterAttributes.followRange).setBaseValue(40D);

 

but the mob continues to look only at the approach of the player into 16 blocks.

 

 

I would examine the changes made to zombies that allows them to path up to 40 blocks or whatever.

 

Essentially the problem is not the 'finding' the player, it is the pathfinding -- most mobs pathfinding is hard-coded to only go out 16 blocks.  Hence, check out the zombie, as Mojang themselves have upped that one to a higher distance.

You are not going to get it that easy as changing the attribute.  You will have to recode part of the mob.