[seqfan] Re: Set of products of two tetrahedrals

[Neil Sloane]

RJM - sure, go ahead and submit them both.  These sequences are
related to some problems that I am working on

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com


On Sun, Nov 29, 2015 at 2:46 PM, Richard J. Mathar <mathar at mpia-hd.mpg.de>
wrote:

> A085780 contains the numbers which are products of two triangular numbers.
>
> Is there any use of adding
> 0, 1, 4, 10, 16, 20, 35, 40, 56, 80, 84, 100, 120, 140, 165, 200, 220,
> 224, 286,
> 336, 350, 364, 400, 455, 480, 560, 660, 680, 700, 816, 840, 880, 969, 1120,
> 1140, 1144, 1200, 1225, 1330, 1456, 1540, 1650, 1680, 1771, 1820, 1960
> and so, defined as numbers that are a product of two tetrahedral numbers?
> That would be the A000292 analogue of A000217.
>
> There is also an equivalent to A140089: the numbers which are a nontrivial
> product of two tetrahedral numbers, meaning both factors must be >1:
> 16, 40, 80, 100, 140, 200, 224, 336, 350, 400, 480, 560, 660, 700, 840,
> 880,
> 1120, 1144, 1200, 1225, 1456, 1650, 1680, 1820, 1960
> from 16=4*4,
> 40=4*10
> 80=4*20
> 100=10*10
> 140=4*35
> 200=10*20
> 224=4*56;
> etc.
>
> RJM
>
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