The counting formula for indecomposable modules over string algebra
Let $ A = 3 Piece Sofa Chaise kQ/I $ be a string algebra.We show that, if for any vertex $ v $ of its bound quiver $ (Q, I) $, there exists at most one arrow (resp.at most two arrows) ending with $ v $ and there exist at most two arrows (resp.at most one arrow) starting with $ v $, then the number of indecomposable modules over $ A $ is $ dim_{k}A+