On a 1040 line 16a is the pensions the same as a retirement 401k?

Yes - if you took a withdrawal from your 401(k) the plan administrator will send you a 1099-R form. You enter the amount of the 401(k) withdrawal on line 16, "Pensions and anuities." If you are subject to the 10% early withdrawal penalty you put that on line 58 "Additional tax on IRAs, other retirement plans, etc." And you show the taxes already withheld on line 62, " Federal income tax withheld from forms W-2 and 1099."