especies combinatóries

[ n·( {a_{k},a_{2}},...,{a_{k+(-1)},a_{1}} ) ]


∑ ( ( n·k )·x^{k} )


[ m·( {a_{k},a_{2}},...,{a_{k+(-1)},a_{1}} ) ]+[ n·( {a_{k},a_{2}},...,{a_{k+(-1)},a_{1}} ) ] = ...
... [ (m+n)·( {a_{k},a_{2}},...,{a_{k+(-1)},a_{1}} ) ]


∑ ( ( (m+n)·k )·x^{k} )
 
f: [n·( {a_{1}},...,{a_{k}} )] ---> [ n·( {a_{k},a_{2}},...,{a_{k+(-1)},a_{1}} ) ] és bijectiva.


f({a_{j}}) = {a_{j+(-1)},a_{j+1}} = {a_{i+(-1),a_{i+1}}} = f({a_{i}})
j+(-1) = i+(-1) & j+1 = i+1
j=i