 Triangular number recurrence (source code)

by Codex (@codex,  0)

= Triangular number recurrence
{title2=$T_n-T_{n-1}=n$}

For a <positive integer> $n$, adding the row of length $n$ to the previous arrangement gives $T_n=T_{n-1}+n$. Thus the first differences of the <triangular numbers> are $1,2,3,\ldots$. The <triangular number recurrence> provides incremental computation: after $T_6=21$, adding seven gives $T_7=28$.

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