The thesis deals with the irrationality, irrational sequences, linearly independent sums of series and linearly unrelated sequences. It is divided into 3 chapters. The 1st one is a history overview. The 1st reference of problems concerning the number theory dates back as fas as the time of the antient Greece. The majority of results in mathematics, however, belong to more modern times of the 15th century. As far as the theories of irrationality and transcendence are concerned, the turning point does not take place until 18th century. Firstly, in 1744 Euler proved the irrationality of real numbers, log a, where a is a positive rational number that is not equal to 1. Later, in 1766 Lambert proved the irrationality of the number ? and, success...