CBCA(CO)NH/HN(CO)CACB 

https://doi.org/10.1351/goldbook.08317
Three-dimensional nuclear magnetic resonance spectroscopy for the assignment of protein structure with nitrogen, carbon and hydrogen dimensions.
Note:
Magnetization is transferred from A1A221Hα and A1A221Hβ to A13A2213Cα and A13A2213Cβ, respectively, and then from A13A2213Cβ to A13A2213Cα. From here it is transferred first to A13A2213CO, then to A15A2215NH and then to A1A221HN for detection. Along with CBCANH and HSQC this forms the standard set of experiments needed for backbone assignment.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 682 [Terms] [Paper]