Primality of 1 Was: Seriously disagreement

[Alonso Del Arte]

> I would not believe _any_ result of someone who thinks that 1 is prime....
>    ...
> Cheers,
> Peter
>

That might tantamount to age discrimination. As late as the 1940s in
America (and perhaps as late as the 1980s in less industrially
developed countries) children were taught that 1 is a prime number.
The OEIS has always acknowledged this, with A008578.

Al



Dear Seqfans,

Root Mean Square (1, 3, ... , 2*K-1) = C   (C,K positive integers)

gives a nice Pell-like equation :

4*K*K - 3*C*C = 1

Solutions :
K = 1 , C = 1
K = 13 , C = 15
K = 181 , C = 209 

Are there other solutions ?

Thanks for comments,

Ctibor