  We prove an explicit combinatorial formula for certain structure constants of
the T-equivariant cohomology of the flag manifold SLn/B. Our result generalizes
the Pieri-type formula in ordinary cohomology proved by Sottile in 1996. Our
result also gives a Pieri-type formula for the double Schubert polynomials
introduced by Lascoux and Schutzenberger.
