They are 1, 3, 6, 10, 15 and 21.
The nth triangular number is n*(n+1)/2.
the fire trangle is the trangle that is on fire
square and Equilateral Trangle
start of david
George Washington
Triangle
180
elizibeth the1st
a+b+c
Kitty hawk, NC
sawnsea
the ipod shuffle
The first month of the year is January. =/