Description: Define the function that maps a positive integer to the set ofFermat
pseudoprimes to the base of this positive integer. Since Fermat
pseudoprimes shall be composite (positive) integers, they must be
nonprime integers greater than or equal to 4 (we cannot use x e. NN/\ x e/ Prime because x = 1 would fulfil this requirement, but
should not be regarded as "composite" integer). (Contributed by AV, 29-May-2023)