\\x=r.2^{n+1}+2^{n}-1\\ 3x+1\\ =3.(r.2^{n+1}+2^{n}-1)+1\\ =3.r.2^{n+1}+3.2^{n}-2\\ (3x+1)/2\\ =3.r.2^{n} +3.2^{(n-1)}-1\\ =3.r.2^{n} +2^{n}+2^{(n-1)}-1\\ =(3.r+1).2^{n}+2^{(n-1)}-1\\ 