Question

1, 3 ,6, 15, 80 , ???

Answer 1

Say me the answer with solution

Answer 2

Follow this method and try it out.  You will have to go to a lengthy process till you get “80” and the next number will be 146.

“The sequence of the triangular numbers comes from the natural numbers (and zero), if you always add the next number:”

1 
1+2=3 

(1+2)+3=6 

(1+2+3)+4=10 

(1+2+3+4)+5=15 

(1+2+3+4+5)+65 = 80

(1+2+3+4+5+65)+66 = 146