Cis trans isomer and cyclic compounds
for calcitriol:

Assuming only Z and E isomer 64 isomers are possible .For rest of isomers (3 ,ZZ,EZ,EE)
each will have 64 isomers.

For Z and E isomer 64 isomers are :


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Quoting 
MARCH’S ADVANCED ORGANIC CHEMISTRY REACTIONS, MECHANISMS,AND STRUCTURE SIXTH EDITION 
Michael B. Smith ,Jerry March