Add Data Validation to columns D:U when there is a name in col A of the same row

I'm trying to add data validation to columns D to U where the only value allowed is either blank or 1, when there is a name in column a of the same row - except column F, it should be allowed to have any whole number greater than or equal to 1.
So far I've recorded a macro and tried to reverse engineer it.... here's what I've got so far, but it doesn't work...

also, since i was there, i was also trying to center the text because it doesn't default that way...

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Any help would be most appreciated.

Thank you in advance.

am i explaining myself enough? or is this just not possible?

it didn't work any better than my code... but i've decided to go a different way with the coding. Thank you for your help.