especies combinatóries: el octopus

[ A_{1},...,A_{j} ]-[ m·( {a_{1}},...,{a_{k}} ) ]


∑ (m·k+j)·x^{k}


[ A_{1},...,A_{j} ]-[ m·( {a_{1}},...,{a_{k}} ) ] + [ B_{1},...,B_{s} ]-[ n·( {a_{1}},...,{a_{k}} ) ] = ...
... [ A_{1},...,A_{j},B_{1},...,B_{s} ]-[ (m+n)·( {a_{1}},...,{a_{k}} ) ]


∑ ( (m+n)·k+(j+s) )·x^{k}


[ A_{1},...,A_{j} ]-[ m·( {a_{1}},...,{a_{k}} ) ] [x] [ B_{1},...,B_{s} ]-[ n·( {a_{1}},...,{a_{k}} ) ] = ...
... [ A_{j} [x] B_{s} ]-[ (ms+nj)·( {a_{1}},...,{a_{k}} ) ]-[ (m·n)·( {a_{k}} [x] {a_{k}} ) ]


∑ ( (m·n)·k^{2}+(ms+nj)·k+(j·s) )·x^{k}