(38G) Fermat Factorization

[Gerald H]

The programme accepts a positive, composite odd number from Ans in the Home screen & returns a factor in Ans.

Fermat's method involves expressing the number to factor as the difference of two different integer squares & so finding two factors.

The only division involved is in the last line of the programme.

Code:



Ans►N:
INT(√Ans)►R:
2*Ans+1►X:
1►Y:
R^2-N►R:
WHILE R
REPEAT
R+X►R:
X+2►X:
DO
R-Y►R:
Y+2►Y:
UNTIL
R≤0
END:
END:
(X-Y)/2: