i want a formula for counting triangles in a big triangle

for example:

http://www.spoj.pl/content/duonghanguyen:tricount.png

level 1=1

level 2=5

level 3=13 and son on>>>

plz help me

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- Jun 30th 2010, 05:58 AMmido22formula for counting triangles
i want a formula for counting triangles in a big triangle

for example:

http://www.spoj.pl/content/duonghanguyen:tricount.png

level 1=1

level 2=5

level 3=13 and son on>>>

plz help me - Jun 30th 2010, 06:16 AMZaph
- Jun 30th 2010, 06:37 AMmido22
thank u very much for quick reply

- Jul 1st 2010, 05:29 PMWilmer
Or go here:

1,4,10,20 - OEIS Search Results - Jul 1st 2010, 08:19 PMsimplependulum
Please check this

When is odd , the formula is

When is even , it is

Or generally the number of triangles we can count is

Or