function factor(n_) {
	n = n_
	a = J(0,2,.)
	if (n<2) {
		return(a)
	}
	else if (n<4) {
		return((n,1))
	}
	else {
		if (mod(n,2)==0) {
			for (i=0; mod(n,2)==0; i++) n = floor(n/2)
			a = a\(2,i)
		}
			
		for (k=3; k*k<=n; k=k+2) {
			if (mod(n,k)==0) {
				for (i=0; mod(n,k)==0; i++) n = floor(n/k)
				a = a\(k,i)
			}
		}
		
		if (n>1) a = a\(n,1)
		return(a)
	}
}