The recurrence cn=4cdotcn−1c_n = 4 \\cdot c_{n-1}cn=4cdotcn−1 with c0=1c_0 = 1c0=1 has closed form:
cn=4nc_n = 4^ncn=4n
cn=4n−1c_n = 4^{n-1}cn=4n−1
cn=n+4c_n = n + 4cn=n+4
cn=ncdot4c_n = n \\cdot 4cn=ncdot4