[seqfan] Re: Sirag numbers.

Harvey P. Dale hpd1 at nyu.edu
Sat Oct 1 15:04:49 CEST 2011

```	I took Jack Brennen's comment, added it to A196224, and
implemented it in a Mathematica program in that sequence.

Best,

Harvey

-----Original Message-----
From: seqfan-bounces at list.seqfan.eu
[mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Jack Brennen
Sent: Thursday, September 29, 2011 12:48 PM
To: seqfan at list.seqfan.eu
Subject: [seqfan] Re: Sirag numbers.

Somebody should let him know that these are really easy
to compute.  Express J*(J+1) in base 4.  If the last two
non-zero digits are either 13 or 33, J is a Sirag number.

For instance, 12*13 == 156, which in base 4 is written as
2130.  Last non-zero digits are '13', so it's a Sirag number.

There are 83334 Sirag numbers <= 10^6, which leads to the
obvious conjecture that the density of Sirag numbers is
1/12.

On 9/29/2011 9:36 AM, Antti Karttunen wrote:
> Not yet in OEIS:
> http://quantumtantra.blogspot.com/2011/08/sirag-numbers.html
>
>
> Cheers,
>
> Antti
>
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> Seqfan Mailing list - http://list.seqfan.eu/
>
>

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