math question "n(n-1)/2"

I could be wrong, but doesn't this formula ensure it can't be a prime number?

I could be wrong, but doesn't this formula ensure it can't be a prime number?

Uggh, been a really long time since I thought about this, but I am wanting to say the n(n-1)/2 has to do with permutations (all possible combinations of possibilities):

http://www.cut-the-knot.org/do_you_k...mutation.shtml

Number theory is a very large part of cryptography and permutation is a way to describe all the possibilties.

Suggest looking into permutations and combinatorics (but be ready for some rather dry reading and some heavy math thinking). I think encryption relies heavily on this stuff (set theory, number theory).

/nebulus

Uggh, been a really long time since I thought about this, but I am wanting to say the n(n-1)/2 has to do with permutations (all possible combinations of possibilities):

http://www.cut-the-knot.org/do_you_k...mutation.shtml

Number theory is a very large part of cryptography and permutation is a way to describe all the possibilties.

Suggest looking into permutations and combinatorics (but be ready for some rather dry reading and some heavy math thinking). I think encryption relies heavily on this stuff (set theory, number theory).

/nebulus

( 3 * (3 - 1) ) / 2 = 3
for n = 3, this function demonstrates a property Karma - you get what you give - and a prime to boot.

( 3 * (3 - 1) ) / 2 = 3
for n = 3, this function demonstrates a property Karma - you get what you give - and a prime to boot.

Now i know why...

Actually it came from arithmetic series where we could assume that

t1 = 0 = 0
t2 = 1 = 0 + 1
t3 = 3 = 0 + 1 + 2
t4 = 6 = 0 + 1 + 2 + 3

where a(initial number) a=0
and the d(differences) d = 1

we put it in arithmetic series formula Sn = (n/2)(2a+(n-1)d)

= (n/2)(2(0)+(n-1)(1))

=(n/2)(n-1)

tn = (n/2)(n-1) :D thanks!