a(n) = Product_{i=1..2*n} (2*i+1).A103639a(n) = Product_{i=1..2*n} (2*i+1).Terms a(0) =1a(1) =15a(2) =945a(3) =135135a(4) =34459425a(5) =13749310575External referencesoeis: A103639