ABSTRACT
For a normed space X we define numerical constants apn(X), 1 ≤ p ≤ ∞, n ∈ N, as follows:
apn(X) := inf { a ∈ R∗; ∀x1, . . . ,xn ∈X, inf
∥∥∥ n∑ i=1
εixi
∥∥∥ ≤ a
( n∑ i=1
‖x‖p )1/p}
.
Definition 6.1.1. We shall say that the normed space X is of infratype p1 if there exists a constant C > 0 such that, apn(X) ≤ C <∞, for all n ∈ N.
