And no, I’m not saying only the chances after a chain of 40. I want to see the chances for every time the chances are increased, because I’m thinking of trying a lower chain because I can’t get to 40
0 8/65536 (1/8192) 1 9/65536 (~1/7282) 2 3 4 5 10/65536 (~1/6554) 6 7 8 9 11/65536 (~1/5958) 10 11 12 12/65536 (~1/5461) 13 14 13/65536 (~1/5041) 15 16 14/65536 (~1/4681) 17 18 15/65536 (~1/4369) 19 20 16/65536 (1/4096) 21 17/65536 (~1/3855) 22 18/65536 (~1/3641) 23 19/65536 (~1/3449) 24 20/65536 (~1/3277) 25 21/65536 (~1/3121) 26 22/65536 (~1/2979) 27 24/65536 (~1/2731) 28 26/65536 (~1/2521) 29 28/65536 (~1/2341) 30 30/65536 (~1/2185) 31 33/65536 (~1/1986) 32 37/65536 (~1/1771) 33 41/65536 (~1/1598) 34 47/65536 (~1/1394) 35 55/65536 (~1/1192) 36 66/65536 (~1/993) 37 82/65536 (~1/799) 38 110/65536 (~1/596) 39 164/65536 (~1/400) 40+ 328/65536 (~1/200)
These are the shiny odds in DP, but Bulbapedia desn't have any for XY, so I believe that they're the same (plus the article says that the chaining mechanics are similar to DP).
Hope this helps! :)