  The divisibility restrictions in the famous equation a n+bn=cn in Fermat Last
Theorem (FLT, 1637) is analyzed how it selects out many triples to be Fermat
triple (i.e. solutions) if n greater than 2, decreasing the cardinality of
Fermat triples. In our analysis, the restriction on positive integer (PI)
solutions ((a,b,c,n) up to the point when there is no more) is not along with
restriction on power n in PI as decreasing sets {PI } containing {odd}
containing {primes} containing {regular primes}, etc. as in the literature, but
with respect to exclusion of more and more c in PI as increasing sets {primes
p} in {p k} in {PI}. The divisibility and co-prime property in Fermat equation
is analyzed in relation to exclusion of solutions, and the effect of
simultaneous values of gcd(a,b,c), gcd(a+b,cn), gcd(c-a,bn) and gcd(c-b,an) on
the decrease of cardinality of solutions is exhibited. Again, our derivation
focuses mainly on the variable c rather than on variable n, oppositely to the
literature in which the FLT is historically separated via the values of power
n. Among the most famous are the known, about 2500 years old, existing
Pythagorean triples (a,b,c,n=2) and the first milestones as the proved cases
(of non-existence as n=3 by Gauss and later by Euler (1753) and n=4 by Fermat)
less than 400 years ago. As it is known, Wiles has proved the FLT in 1995 in an
abstract roundabout way. The n<0, n:=1/m, as well as complex and quaternion
(a,b,c) cases focusing on Pythagoreans are commented. Odd powers FLT over
quaternions breaks.
