Behold! (1 × 2) + (2 × 3) + ⋯+ n × (n + 1) = (1/3) (n + 1) 3 - (n + 1)]

Ali. R. Amir-Moez
1987 The College Mathematics Journal  
Scheme 1. Metathesis reactions affording; (1) [Cu(CH3CN)3.5][FAl] (1) with alternating [Cu(CH3CN)3] + and [Cu(CH3CN)4] + complex cations and (2,3) [Cu(CH3CN)4][TEF] (2).
doi:10.2307/2686803 fatcat:4v47so7j7ja6jk23vxrfw2w6qe