Published online by Cambridge University Press: 20 November 2018
A sequence, a 1 < a 2 < a 3 < …, of positive integers is called lacunary if the difference sequence dn = a n+l — an tends to infinity as n → ∞.
In several recent papers we have made use of these sequences in analysis and combinatorics. In [6] we show that the class of all sets which are either finite or the range of a lacunary sequence is “full” in the sense that if (tk) is a real sequence and
for each
then (tk ) is an l1 sequence, that is,
In [3] the class of all finite unions of sets of
is shown to consist of exactly those sets of integers, A, whose characteristic sequence, χA , is in the well known summability space bs + c 0. More recently, in [1], we study lacunary sequences in connection with the conjecture of P.