a(n) = (7*n)!/((5*n)!*n!^2).A273628a(n) = (7*n)!/((5*n)!*n!^2).Terms a(0) =1a(1) =42a(2) =6006a(3) =1085280a(4) =217567350a(5) =46262007792External referencesoeis: A273628