#### English Title

On forms of the type *mxx*+*nyy* for exploring prime numbers by idoneals of them with remarkable properties

#### Enestrom Number

708

#### Fuss Index

32

#### Original Language

Latin

#### Content Summary

"If *m* and *n* are positive numbers and if *N* is contained in two different manners in the form *mxx*+*nyy*, so that *N* = *maa*+*nbb* and *N* = *mcc*+*ndd*, in reducing the fraction (*a*±*c*)/(*b*±*d*) to its lowest terms, then the fraction (*mpp*)/(*nqq*) = *r*/*s*; in the case *r*+*s* is an odd number, it will be a factor of the number *N*; if it is even, then its half, (*r*+*s*)/2 will be a factor of that number *N*. From this, it follows that any number contained in more than one fashion in the form *mxx*+*nyy* will be a composite, or non-prime number." Euler goes on to define "congruent" numbers, describe their properties, and then give the famous list of the 65 congruent numbers, all less than 10,000. Feuter warns that the proofs of Theorems 6, 8, and 9 are "not rigorous."

#### Published as

Journal article

#### Published Date

1801

#### Written Date

1778

#### Original Source Citation

Nova Acta Academiae Scientiarum Imperialis Petropolitanae, Volume 12, pp. 22-46.

#### Opera Omnia Citation

Series 1, Volume 4, pp.269-289.

#### Record Created

2018-09-25