[seqfan] Re: (no subject)
Raff, Paul
praff at math.rutgers.edu
Mon Nov 9 16:52:34 CET 2009
Hi Ctibor,
I think you mean the following (with modification in caps):
a(n)= ceiling(SQRT(n*(n+1)/2))^2 - n*(n+1)/2
[paul]
---
Paul Raff
Postdoctoral Researcher - Cognitive Assistants as Analysts' Deputies
School of Communication and Information
Rutgers University
http://www.myraff.com
Work: (732) 932-7500 x8023
Mobile: (704) 604-2154
---
On Mon, Nov 9, 2009 at 10:42 AM, <c.zizka at email.cz> wrote:
> Dear seqfans,
>
> let a(n) is the difference between n-th triangular number and next perfect
> square (submitted to OEIS today).
>
> a(n)= (ceiling(n*(n+1)/2))^2 - n*(n+1)/2
>
> Interestingly a(n) takes values {0,1,3,4,6,8,9,10,13,15,16,19,21,22,...}
> and it seems no a(n) is from {2,5,7,11,12,14,17,18,20,23,...} .
> In OEIS we can found for a(n)=0 A001108, for a(n)=1 A006451, for a(n)=3
> A154138, for a(n)=4 A154139 , for a(n)=6 A154140, for a(n)=8 A154141,
> for a(n)=9 A154142, for a(n)=10 A154143.
>
> Why can not be :
>
> (ceiling(n*(n+1)/2))^2 = 2+ n*(n+1)/2
>
> :-)
>
> Ctibor
>
>
>
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