Maybe one additional note: When we access elements of an array, that generally occurs with an offset to stackpointer. Stackpointer is generally fixed while we are inside a proc, and stackpointer is generally located in a register, so to access an array element a offset plus stackpointer is used to locacte the array element. If array index is a constant, then offset is constant too. If array index is a variable, than offset is product of element_size and offset. So there is a runtime mul in later case.
To access an element of a seq, there is some indirection: First the base address of the pointer to payload is moved into a CPU register, and an offset = (elementsize * index) is added to locate element. When we access many elements of a seq, then only one time its payload address needs to be moved into a CPU register, so accessing many elements is not really slower for seq than it is for array.
