  A natural number is called an {\lambda}-parasitic number if it is multiplied
by integer {\lambda} as the rightmost digit moves to the front. The Full set of
these numbers is known in the decimal system. Here, a formula to analytically
generate parasitic numbers in any base was derived and demonstrated for the
number systems in base t = 3, 4, 5, 8, 10 and 16. It allows to generate
parasitic numbers with given numbers of periods. The formula was derived using
the definition of parasitic numbers , not their cyclical property.
