The 9j symbol may be defined either in terms of 3j symbols or equivalently in terms of 6j symbols:
The 9j symbol may also be written as a finite triple sum equivalent to a terminating generalized hypergeometric series of three variables with unit arguments. See Srinivasa Rao and Rajeswari (1993, pp. 7 and 125–132) and Rosengren (1999).