This question already has an answer here:
Triangle numbers are $0,1,3,6,10...$ And square numbers are $0,1,4,9,16...$ $N$'th triangle no. = $N(N+1)/2$ $N$'th square no. = $N\cdot N$
So I was wondering are there any numbers which are in both these lists apart from $0,1$??
I found one using trial and error that is $36$ which is the $8$'th triangular number and $6$'th square number. Are there more? What is the algebraic method to calculate them?? thanks in advance.