is this n! (n-factor)? - Science, Math and Philosophy Forum

Two Plus Two Forums Other Topics Science, Math, and Philosophy

is this n! (n-factor)?

Post Reply Subscribe

...

12-12-2014 , 05:37 PM

rivercitybirdie

Pooh-Bah

Join Date: May 2012 Posts: 4,707

sorry, i haven't looked at this in 30+ years... i did cursory google and didn't get my answer quickly.

is this n! (n-factor)?

n!(5) = 4 + 3 +2 + 1 = 10... sum of positive integers smaller than it.

took me forever to think of this... i think it's right but not sure

thanks in advance!

Quote

12-12-2014 , 06:30 PM

Aaron W.

Carpal \'Tunnel

Join Date: Sep 2002 Posts: 30,132

Quote:

Originally Posted by rivercitybirdie

Quote

12-12-2014 , 09:17 PM

FWWM

FOOT FF Fristion '15

Join Date: Oct 2013 Posts: 12,502

n! includes n as posted in the link before

Quote

12-13-2014 , 01:13 PM

heehaww

Pooh-Bah

Join Date: Aug 2011 Posts: 5,081

Quote:

Originally Posted by rivercitybirdie

4 + 3 +2 + 1 = 10... sum of positive integers smaller than it.

Sum of positive ints smaller than n = n(n-1)/2 = C(n,2) where the C() is combinations. Combinations of 2 are also called triangular numbers. So for instance, the sum there is 10 = C(5,2)

Quote

Post Reply Subscribe

...