Synthesising every natural still life

[squareroot12621]

xs31_69b88ci6zciq3qq1 in an absolutely horrendous 20G:

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Reduced to 19g with almost as horrendous 3g synth of the loaf-blinker pair

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For something less messy in a future reduction, these loaf+block pairings from the synthesis above are also 3g in cost

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18G by replacing the 3-glider 3o$3bo! spark with a similar 2-glider collision: ⵌgliderˍsynthesis ⵌ18gˍsynthesis ⵌstillˍlife ⵌpopulationˍ31

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x = 237, y = 77, rule = B3/S23
155bo$156b2o$155b2o14$99bo$99bobo$99b2o$84bo$82bobo$83b2o3$81bo17bo$79b
obo17bobo$80b2o17b2o$204b2o$204b2o4$72bo$2bo70bo128b2ob2o$obo68b3o22b
o105b2ob2o3bo$b2o93bo113bo$96bo113bo$7bo3b3o74b2o112b2o$8bo2bo75bo2bo
110bo2bo$6b3o3bo74bobo111bobo$88bo104b2o7bo$193b2o8$68b3o$70bo$69bo115b
2o$184bobo$186bo6bo$193b2o$192bobo2$212bo$189b2o20b2o$190b2o19bobo$189b
o$204b2o$203b2o$205bo4$185b3o24b2o$187bo24bobo$186bo25bo5$234b2o$234b
obo$234bo!

[I6_I6]

xs31_69b88ci6zciq3qq1 in an absolutely horrendous 20G:
[...]

[...]

18G by replacing the 3-glider 3o$3bo! spark with a similar 2-glider collision:[size
[...]

16G using cheaper pi and cleanup:

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x = 80, y = 68, rule = B3/S23
52bo$50b2o$51b2o$45bo$46b2o$45b2o3$42bo9bo$43b2o5b2o$42b2o7b2o2$o$b2o
$2o50b3o$11bo$10b2o26bobo4b2o$5bobo2bobo25b2o4bo2bo$6b2o31bo4bobo$6bo
38bo6$33b2o$34b2o$33bo7b2o$40bobo$42bo2$49b2o$37b3o9bobo$39bo9bo$38bo
$41b3o$41bo$42bo3$34bo$34b2o$33bobo11$56b2o$56bobo$56bo10$78b2o$77b2o
$79bo!

ⵌgliderˍsynthesis ⵌ15gˍsynthesis ⵌstillˍlife ⵌpopulationˍ31
EDIT:
Much cleaner, 15G:

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x = 109, y = 39, rule = B3/S23
52bo$52bobo$52b2o$49bo$47bobo$48b2o48b2o$98b2o2$46bo5bo$44bobo5bobo$45b
2o5b2o$o95b2ob2o$b2o52bo40b2ob2o$2o53bo47b3o$11bo43bo$10b2o35b2o28bo18b
2o$5bobo2bobo24bo8bo2bo28bo16bo2bo$6b2o30bo7bobo27b3o16bobo$6bo29b3o8b
o48bo2$83bo$33b3o48bo$35bo46b3o$34bo2$85bo$85b2o$84bobo$90b3o$92bo$91b
o2$101b3o$101bo$102bo2$107bo$106b2o$106bobo!

[Anivec]

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x = 109, y = 39, rule = B3/S23
52bo$52bobo$52b2o$49bo$47bobo$48b2o48b2o$98b2o2$46bo5bo$44bobo5bobo$45b
2o5b2o$o95b2ob2o$b2o52bo40b2ob2o$2o53bo47b3o$11bo43bo$10b2o35b2o28bo18b
2o$5bobo2bobo24bo8bo2bo28bo16bo2bo$6b2o30bo7bobo27b3o16bobo$6bo29b3o8b
o48bo2$83bo$33b3o48bo$35bo46b3o$34bo2$85bo$85b2o$84bobo$90b3o$92bo$91b
o2$101b3o$101bo$102bo2$107bo$106b2o$106bobo!

Where did the block go?