1.
1->1&2->2&3->3
4->5(2+3)...1111,22,121,211,112
5->8(3+5)...11111,221*3,1112*4
6->13(5+8)...111111,222,2211*C4¨ú2,21111*5
7->21(8+13)

2.
else return step(x-1) + step(x-2)