The Hubbard model for the square planar lattice in the limit t/U<<1 is discussed. The ground state is chosen to be the product of the Hubbard model's exact solutions for four-site blocks. One-particle excitations appear to be Fermi particles with spin ¹/₂. Their effective mass near the bottom of the band coincides with the effective mass of excitations in the paramagnetic state in the 'Hubbard-I' approximation. However, minima of the spectrum are situated at other points in the Brillouin zone. The possibility of the binding of two excitations into singlet pair with charge 2e is demonstrated. Cohesive energy is calculated to be equal to 0.1t. The superfluid state of the Bose gas of such pairs is assumed to be connected with high-T_c superconductivity.