how to write the elements of the triangle of Pascal so that all 1 are aligned on a same vertical. Thank you.

restart;
with(geometry);
with(plots);
_EnvHorizontalName = 'x';
_EnvVerticalName = 'y';
point(A, -3, 9);
point(B, -5, 0);
point(C, 6, 0);
xA := -3;
yA := 9;
xB := -5;
yB := 0;
xC := 6;
yC := 0;
triangle(ABC, [A, B, C]);
midpoint(M2, A, C);
midpoint(M1, B, C);
midpoint(M3, A, B);
coordinates(M1);
coordinates(M2);
coordinates(M3);
segment(sA, [A, M1]);
segment(sB, [B, M2]);
segment(sC, [C, M3]);
centroid(G, ABC);
midpoint(J1, A, G);
midpoint(J2, B, G);
midpoint(J3, C, G);
coordinates(J1);
coordinates(J2);
coordinates(J3);
zA := xA + yA*I;
zB := xB + yB*I;
zC := xC + yC*I:
diff((z - zA)*(z - zB)*(z - zC), z)*I;);
allvalues(%, z)
;I am trying to find focus of Steiner ellipse with Marden's theoreme. Thank you.

I would like to apply the pappus theorem to an ellipse. Pascale's theorem 

I am trying to decompose an isprime into sum of 2 squares.
Can you tell me why yhse procedure are not goog.
                       

Sumof2Squares:= proc(p::And(prime, satisfies(p-> irem(p,4)=1)))
local x, y:= 1;
   x:= mods(Roots(x^2+y^2), p)[2,1];
   while x^2+y^2 > p do
      (x,y):= FermatDescent(x,y,p)
   end do;
   (x,y)
end proc:

FermatDescent:= proc(x::posint, y::posint, p::posint)
local 
   m:= (x^2+y^2)/p,
   a:= mods(x,m),  
   b:= mods(y,m);

   (abs((a*x+b*y)/m), abs((a*y-b*x)/m))
end proc:
   
trace(FermatDescent);

Sumof2Squares(1973);
Thank you.

I should like to find the list of Friday 13 of a year