Răspuns:
Efectiv faci calcule, tinand cont ca suma respectiva este
A(1)+A(2)+...A(n)=(1 1 1) + (2 1 1) +.... +. (n 1 1) =
( 1 1 1 ) ( 1 2 1) ( 1 n 1)
( 1 1 1 ) ( 1 1 2) (1 1 n)
= ((1+2+...n) n n) (n(n+1)/2 n n)
(n (1+2+...n) n) = (n n(n+1)/2 n)
(n n (1+2+...+n)) (n n n(n+1)/2)
((n+1)/2 1 1)
= n× (1 (n+1)/2 1) = nA( (n+1)/2)
(1 1 (n+1)/2)
