The ancient greeks were very interested in number patterns. triangular numbers are number that can be represented by a triangular array of dots, with n dots on each side. the first three triangular numbers are 1, 3, and 6.
write a formula for the nth term of this sequence.
a) an= 2n
b) an= n^2/2
c) an= n(n+1)/2
d) an= n+1/2