a2b=numere pare; a≠0; b=cifra para⇒b=(0,2,4,6,8)
a=(1,2,3,4,5,6,7,8,9)
120,122,124,126,128; 220,222,224,226,228; 320; 322, 324, 326, 328; 420, 422, 424, 426,428; 520, 522,524,526,528; 620, 622, 624,626,628,720, 722, 724,726,728; 820, 822,824,826, 828,920,922,924,926, 928.
