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Reference request: Set of n-Multisets of elements in $mathbbN$ is countable set


Why does mathematical convention deal so ineptly with multisets?Is $cap_n=1^infty left( mathbbR setminus A_n right) $ countable set?Prove that there exists a countable collection of rectangles in $mathbbR^n$Multisets and cardinalityAlgorithm for generating the intersection of two multisetsIs there a name for the infinite sequence of k-multisets with one element, two elements, etc.?Can I use inclusion symbol to address a multiset's elements?Arranging $mathbb N$ into a two-dimensional array to prove a countably infinite collection of countable sets is countable.Category of Multisets and SpansProof for bijection between the set of k-multisets & the set of k-subsets.













0












$begingroup$


Let $n in mathbbN$ be fixed. I need a reference for the statement, that the collection of multisets of length $n$ with elements in $mathbbN$
beginequation
M_mathbbN = a_i in mathbbN
endequation

is a set and is countable.










share|cite|improve this question











$endgroup$











  • $begingroup$
    There is a surjection from the finite sequences onto multisets.
    $endgroup$
    – Asaf Karagila
    2 days ago















0












$begingroup$


Let $n in mathbbN$ be fixed. I need a reference for the statement, that the collection of multisets of length $n$ with elements in $mathbbN$
beginequation
M_mathbbN = a_i in mathbbN
endequation

is a set and is countable.










share|cite|improve this question











$endgroup$











  • $begingroup$
    There is a surjection from the finite sequences onto multisets.
    $endgroup$
    – Asaf Karagila
    2 days ago













0












0








0





$begingroup$


Let $n in mathbbN$ be fixed. I need a reference for the statement, that the collection of multisets of length $n$ with elements in $mathbbN$
beginequation
M_mathbbN = a_i in mathbbN
endequation

is a set and is countable.










share|cite|improve this question











$endgroup$




Let $n in mathbbN$ be fixed. I need a reference for the statement, that the collection of multisets of length $n$ with elements in $mathbbN$
beginequation
M_mathbbN = a_i in mathbbN
endequation

is a set and is countable.







discrete-mathematics elementary-set-theory multisets






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited 2 days ago









Asaf Karagila

306k33438769




306k33438769










asked 2 days ago









warpfelwarpfel

1067




1067











  • $begingroup$
    There is a surjection from the finite sequences onto multisets.
    $endgroup$
    – Asaf Karagila
    2 days ago
















  • $begingroup$
    There is a surjection from the finite sequences onto multisets.
    $endgroup$
    – Asaf Karagila
    2 days ago















$begingroup$
There is a surjection from the finite sequences onto multisets.
$endgroup$
– Asaf Karagila
2 days ago




$begingroup$
There is a surjection from the finite sequences onto multisets.
$endgroup$
– Asaf Karagila
2 days ago










1 Answer
1






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0












$begingroup$

There is a bijection $mathcalM_mathbbN rightarrow bigcup_k=0^inftymathbbN^k$. Now each $mathbbN^k$ is countable and countable unions of countable sets are again countable.






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    0












    $begingroup$

    There is a bijection $mathcalM_mathbbN rightarrow bigcup_k=0^inftymathbbN^k$. Now each $mathbbN^k$ is countable and countable unions of countable sets are again countable.






    share|cite|improve this answer









    $endgroup$

















      0












      $begingroup$

      There is a bijection $mathcalM_mathbbN rightarrow bigcup_k=0^inftymathbbN^k$. Now each $mathbbN^k$ is countable and countable unions of countable sets are again countable.






      share|cite|improve this answer









      $endgroup$















        0












        0








        0





        $begingroup$

        There is a bijection $mathcalM_mathbbN rightarrow bigcup_k=0^inftymathbbN^k$. Now each $mathbbN^k$ is countable and countable unions of countable sets are again countable.






        share|cite|improve this answer









        $endgroup$



        There is a bijection $mathcalM_mathbbN rightarrow bigcup_k=0^inftymathbbN^k$. Now each $mathbbN^k$ is countable and countable unions of countable sets are again countable.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 2 days ago









        An_876_JokeAn_876_Joke

        1036




        1036



























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