sum of square is equal to prime












0












$begingroup$


Let $n in mathbb{N}$ and $p$ a prime number then I would like to find all $(a_1, ..., a_n) in mathbb{N}^n$ such that :
$$sum a_i^2 = p$$



Using a computer program It seems that the only solutions are $(1,...,1)$.



I don't see how to prove this result. An idea could be to look at the whole expression mod $4$, but it doesn't seem to help... :(










share|cite|improve this question









$endgroup$








  • 4




    $begingroup$
    There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
    $endgroup$
    – lulu
    Dec 11 '18 at 15:51






  • 1




    $begingroup$
    Fermat's two square Theorem is relevant.
    $endgroup$
    – lulu
    Dec 11 '18 at 15:53










  • $begingroup$
    See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 16:12


















0












$begingroup$


Let $n in mathbb{N}$ and $p$ a prime number then I would like to find all $(a_1, ..., a_n) in mathbb{N}^n$ such that :
$$sum a_i^2 = p$$



Using a computer program It seems that the only solutions are $(1,...,1)$.



I don't see how to prove this result. An idea could be to look at the whole expression mod $4$, but it doesn't seem to help... :(










share|cite|improve this question









$endgroup$








  • 4




    $begingroup$
    There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
    $endgroup$
    – lulu
    Dec 11 '18 at 15:51






  • 1




    $begingroup$
    Fermat's two square Theorem is relevant.
    $endgroup$
    – lulu
    Dec 11 '18 at 15:53










  • $begingroup$
    See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 16:12
















0












0








0





$begingroup$


Let $n in mathbb{N}$ and $p$ a prime number then I would like to find all $(a_1, ..., a_n) in mathbb{N}^n$ such that :
$$sum a_i^2 = p$$



Using a computer program It seems that the only solutions are $(1,...,1)$.



I don't see how to prove this result. An idea could be to look at the whole expression mod $4$, but it doesn't seem to help... :(










share|cite|improve this question









$endgroup$




Let $n in mathbb{N}$ and $p$ a prime number then I would like to find all $(a_1, ..., a_n) in mathbb{N}^n$ such that :
$$sum a_i^2 = p$$



Using a computer program It seems that the only solutions are $(1,...,1)$.



I don't see how to prove this result. An idea could be to look at the whole expression mod $4$, but it doesn't seem to help... :(







number-theory






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Dec 11 '18 at 15:49









hdfjhqzuifqhhdfjhqzuifqh

1




1








  • 4




    $begingroup$
    There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
    $endgroup$
    – lulu
    Dec 11 '18 at 15:51






  • 1




    $begingroup$
    Fermat's two square Theorem is relevant.
    $endgroup$
    – lulu
    Dec 11 '18 at 15:53










  • $begingroup$
    See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 16:12
















  • 4




    $begingroup$
    There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
    $endgroup$
    – lulu
    Dec 11 '18 at 15:51






  • 1




    $begingroup$
    Fermat's two square Theorem is relevant.
    $endgroup$
    – lulu
    Dec 11 '18 at 15:53










  • $begingroup$
    See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
    $endgroup$
    – Robert Israel
    Dec 11 '18 at 16:12










4




4




$begingroup$
There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
$endgroup$
– lulu
Dec 11 '18 at 15:51




$begingroup$
There are lots of examples...$1^2+2^2=5$, say. Or $2^2+3^2=13$. Did you have some specific thing in mind?
$endgroup$
– lulu
Dec 11 '18 at 15:51




1




1




$begingroup$
Fermat's two square Theorem is relevant.
$endgroup$
– lulu
Dec 11 '18 at 15:53




$begingroup$
Fermat's two square Theorem is relevant.
$endgroup$
– lulu
Dec 11 '18 at 15:53












$begingroup$
See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
$endgroup$
– Robert Israel
Dec 11 '18 at 16:12






$begingroup$
See OEIS sequence A001156 for the number of partitions of a given positive integer into squares.
$endgroup$
– Robert Israel
Dec 11 '18 at 16:12












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