I just checked Wiki and yes, Laffer worked for Reagan - it does not mention Carter. Laffer is a conservative, of course, so not certain why he would work for Carter, but it appears he did not.
You may be right about the Carter years. Laffer was the first chief economist at the OMB, over the years 1970-72, Nixon era actually. He was a consultant to the likes of William Simon, George Schultz and Don Rumsfeld but that was all before 1977.
The claim that he worked for Reagan is misleading. I was a Laffer fan back then (not so much now) and was disappointed when he wasn’t working for Reagan. The closest he came to working for Reagan is being one member of an outside non-governmental advisory committee. During Reagan, Laffer ran his own private sector firm, Laffer Associates, which he founded in 1979 before Reagan was even elected.
Laffer is a misleading character and one I don’t trust. He has publicly acknowledged that he voted for Clinton, twice, and for Obama. Yet he constantly lets people call him a conservative. He lets people say things about him that he knows to be patently untrue and he never corrects them. I don’t find him honest.