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rho1(n)= { local(x = 2,y = 5); while(gcd(y-x,n) == 1, x = (x^2+1)%n; y = (y^2+1)%n; y = (y^2+1)%n ); gcd(n, y-x) } rho2(n)= { local(m = rho1(n)); if (isprime(m), print(m), rho2(m)); if (isprime(n/m), print(n/m), rho2(n/m)); } rho(n)= { local(m = factor(n,0)); print(m); m = m[,1]; n = m[#m]; if (!isprime(n), rho2(n)); } rhobrent(n)= { local(x,y,x1,k,l,p,c,g); x1 = x = y = 2; k = l = p = 1; c = 0; while (1, x=(x^2+1)%n; p=(p*(x1-x))%n; c++; if (c==20, if (gcd(p,n)>1, break); y = x; c = 0 ); k--; if (!k, if (gcd(p,n)>1, break); x1 = x; k = l; l <<= 1; for (j=1,k, x = (x^2+1)%n); y = x; c = 0 ) ); until (g != 1, y = (y^2+1)%n; g = gcd(x1-y,n) ); if (g==n, error("algorithm fails")); g }