[seqfan] Re: C(2n,n) - n^2 and C(n^2,n) - n^n

Hugo Pfoertner yae9911 at gmail.com
Wed Mar 21 22:42:32 CET 2018


(i) (PARI)
 for(n=1000,20000,if(ispseudoprime(binomial(n+n,n)-n^2),print1(n,", ")))
produces
1301, 2263, 5189,

Hugo Pfoertner

On Wed, Mar 21, 2018 at 5:50 PM, Harvey P. Dale <hpd at hpdale.org> wrote:

>         The next term in sequence (i) is 1301.
>         Best,
>         Harvey
>
>
> -----Original Message-----
> From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of ????
> ?????????
> Sent: Tuesday, March 20, 2018 2:00 PM
> To: Michael De Vlieger <seqfan at list.seqfan.eu>
> Subject: [seqfan] C(2n,n) - n^2 and C(n^2,n) - n^n
>
> Dear SeqFans, numbers n such that:
> (i) C(2n,n) - n^2 is prime: 2, 3, 5, 9, 13, 27, 47, 59, 111, 547, 923, ...
> (ii) C(n^2,n) - n^n is squarefree: 2, 3, 5, 7, 13, 17, 19, 23, 29, 31, 33,
> 35, 37, 41, 43, 47, 53,...
> What tn the next one? Thanks. JSG
>
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