T(n)^2=T(T(n))+T(T(n)-1)
From specialfunctionswiki
Theorem
The following formula holds for $n=2,3,4,\ldots$: $$T(n)^2=T(T(n))+T(T(n)-1),$$ where $T(n)$ denotes the $n$th triangular number.
The following formula holds for $n=2,3,4,\ldots$: $$T(n)^2=T(T(n))+T(T(n)-1),$$ where $T(n)$ denotes the $n$th triangular number.
