restul=50 => 50<ab<100
ab cub perfect => ab=64
100≤n<1000
n=64•c+50
100≤64c+50<1000
50≤64c<950
50<64•1; 64•14=896<950; (64•15>950)
cel mai mic n=64•1+50=114
cel mai mare n=64•14+50=946
Suma =64•1+50+64•2+50+64•3+50+….+64•14+50
Suma =64(1+2+3+…+14)+14•50
Suma =64•14•15/2 +14•50
Suma =960•7+700
Suma=7420 (suma nr naturale de 3 cifre care împărțite la ab dau restul 50)
