(7-1)(7+1)(7^2+1)(7^4+1)*(7^8+1)-7^16+23

6*8(49+1)*(7^4+1)(7^8+1)-7^16+23

2400(7^4+1)(7^8+1)-7^16+23

(2400*7^4+2400)(7^8+1)-7^16+23 = 2400*7^12+2400*7^4*2400*7^8-7^16+23 = 2400*7^12+2400*2401+2400*7^8+2423-7^16 = 2400*7^12+5762400+2400*7^8+2423-7^16 = 2400*7^12+5764823+2400*7^8-7^16 = 22