A 20 tone well tempered nonet (20WTN) is related to well temperaments of 17edo and 18edo, but with a nonet rather than the 2/1 being constant. Its patent tunings alternate division of the just perfect fifth into 10 equal parts (10EDF) with sequences of ten equal steps of 60 to 80 cents each. This will create ten equally-spaced intervals between an interval between 600 and 800 cents and the just perfect fifth.

Optimal Intervals

Target a Target b
1 70.1955
2 140.391
3 210.5865
4 280.782
5 350.9775
6 421.173
7 491.3685
8 561.564
9 631.7595
10 701.955
11 773.104 764.2106
12 844.254 826.466
13 915.403 888.7219
14 986.552 950.9775
15 1057.701 1013.2331
16 1128.896 1075.48875
17 1200 1137.7444
18 1271.1493 1200
19 1342.2986 1262.2556
20 1413.4479 1324.511