This question concerns the recurrence relation for$$an$=$an$=$the number of ways to climb to the nth$$stair$,$ if stairs can only be climbed two or three at a time.$[$Assume stairs are numbered$1,2,3,....]$

Question:$$ What are the initial conditions for the recurrence $?$

Question $10$Answer

a$.$

a$1=1$a$2=1,$a$3=2$a$1=1$a$2=1,$a$3=2$

b$.$

a$1=0,$a$2=1,$a$3=2$a$1=0,$a$2=1,$a$3=2$

c$.$

a$1=0$a$1=0$

d$.$

a$1=0,$a$2=1,$a$3=1$