I thought the following would work but org seems to reorder the vector:

  | t | y_t |  0.9^t | y_{t+1} |
  |---+-----+--------+---------|
  | 1 | 115 |    0.9 |     0.9 |
  | 2 | 121 |   0.81 |    2.52 |
  | 3 | 118 |  0.729 |   4.707 |
  | 4 | 127 | 0.6561 |  7.3314 |
  #+TBLFM: $3=0.9^$1::$4=(@2$3..@0$3)*(@0$1..@2$1)

but maybe this will point you somewhere useful...

-- 
: Eric S Fraga (0xFFFCF67D), Emacs 25.1.1, Org release_9.0.5-391-g36c7cf