especies combinatóries

[ n·( {a_{1}},...,{a_{k}} ) ]


∑ ( ( n·k )·x^{k} )


[ m·( {a_{1}},...,{a_{k}} ) ] + [ n·( {a_{1}},...,{a_{k}} ) ] = [ (m+n)·( {a_{1}},...,{a_{k}} ) ]


∑ ( ( (m+n)·k )·x^{k} )


[ m·( {a_{1}},...,{a_{k}} ) ] [x] [ n·( {a_{1}},...,{a_{k}} ) ] = ...
... [ (m·n)·( {a_{k}} [x] {a_{k}} ) ]


∑ ( ( (m·n)·k^{2} )·x^{k} )