The Diophantine equation x2+C=yn, in positive integers unknowns x, y and n, has a long story. The first case to have been solved appears to be c=1. In 1850 Victor Lebesgue showed, using a elementary factorization argument, that the only solution is x=0, y=1. Over the next 140 years many equations of the form x2+C=yn have been solved using the Lebesgue’s elementary trick. In 1993 John Cohn published an exhautive historical survey of this equation which completes the solution for but all 23 values of C in the range 1 ≤ C ≤ 100.