# A089539 (b-file synthesized from sequence entry) 1 4 2 4 3 9 4 25 5 121 6 721 7 5041 8 40321 9 362885 10 3628801 11 39916803 12 479001617 13 6227020801 14 87178291201 15 1307674368007 16 20922789888002 17 355687428096003 18 6402373705728023 19 121645100408832001 20 2432902008176640001 21 51090942171709440011 22 1124000727777607680029 23 25852016738884976640003