Generate list of random numbers (1 to 6) without repeating last and second last number?

Try this

Assuming A1 is blank or a text header then use this formula in A2

=RANDBETWEEN(1,6)

and then this formula in A3 copied down as far as you want

=AGGREGATE(15,6,{1,2,3,4,5,6}/(COUNTIF(A1:A2,{1,2,3,4,5,6})=0),RANDBETWEEN(1,6-COUNT(A1:A2)))