Blackjack

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Blackjack
x = 25, y = 13, rule = B3/S23 18b2o$5b2o11b2o$5b2o$bo13b2o$obo12bo$2o4b2o4b6o$6bobo4b4o$5bo2bo5bo8b 2o$6b2o14bobo$6bo16bo$18b2o$5b2o11b2o$5b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ GPS 10.5 THUMBSIZE 2 ZOOM 10 ]]
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Pattern type Oscillator
Number of cells 40
Bounding box 25 × 13
Period 21 (mod: 21)
Heat 20.2
Volatility 0.88 | 0.88
Kinetic symmetry n
Discovered by iNoMed
Chris857
Mitchell Riley
Year of discovery 2025

Blackjack (also called 40p21 or 42p21) is a period-21 oscillator. It was found by iNoMed on May 21, 2025 from a CatForce partial file "earliercensus_1_0_econtransp_2cat_trimmed.rle" created by Mitchell Riley from August 4, 2023.[1][2] It consists of two copies of an R-pentomino being hassled by a boat, two stationary blocks, and a sacrificial block. It is a block factory; with two copies of the R-pentomino, the created extra block in one half is used as a sacrificial block in the other half.

Two offsets work. The first form that was found had the two halves 10 (or 11) generations apart. Later the same day, Chris857 found a form with the two halves 8 (or 13) generations apart[3]; this is the form in the infobox above. The 10+11 form has a minimum population of 42 cells, while the 8+13 form has a minimum population of 40 cells.

The name "blackjack" comes from the game, where the highest score is 21, and a blackjack in the game is made of a 10-point card and an 11-point card (an ace). This name was proposed when only the 10+11 form was known.

Chris857 found a 22-glider synthesis for both forms on the same day as the oscillator's discovery,[4][5] which he reduced to 21 gliders on May 23.[4][6] On June 7, 2025, KtT lowered the cost to 20 gliders.[7][8]

x = 34, y = 25, rule = B3/S23 7b2o19b2o$7bobo18bobo$8bo20bo3$2o3bo4b2o9b2o3bo4b2o$2ob2ob2o2b2o9b2ob 2ob2o2b2o$4bo2bo17bo2bo$5b2o19b2o4$7bo$6b2o19b3o$5b3o19b2o$6b4o16bo3bo $6b2obo17bobo$7bo21bo$b2o8b2o9b2o8b2o$b2o8b2o9b2o8b2o3$4bo20bo$3bobo 18bobo$4b2o19b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBNAIL HEIGHT 500 WIDTH 600 GPS 21 ZOOM 16 THEME Book STARTFROM 21 ]]
Both versions side by side. 8+13 on left, 10+11 on right.
(click above to open LifeViewer)
Catagolue: here


See also

References

  1. ↑ iNoMed (May 21, 2025). Re: Oscillator Discussion Thread (discussion thread) at the ConwayLife.com forums
  2. ↑ https://discord.com/channels/357922255553953794/370571014654001154/1374996009326743672
  3. ↑ rabbit (May 21, 2025). Re: Oscillator Discussion Thread (discussion thread) at the ConwayLife.com forums
  4. ↑ 4.0 4.1 Chris857 (May 21, 2025). Re: Synthesising oscillators (discussion thread) at the ConwayLife.com forums
  5. ↑ shinjuku (#10112065177) (May 22, 2025). Job triggered by Adam P. Goucher at GitLab Catagolue project.
  6. ↑ shinjuku (#10128096743) (May 23, 2025). Job triggered by Adam P. Goucher at GitLab Catagolue project.
  7. ↑ KtT (June 7, 2025). Re: Synthesising oscillators (discussion thread) at the ConwayLife.com forums
  8. ↑ shinjuku (#10285154482) (June 7, 2025). Job triggered by Adam P. Goucher at GitLab Catagolue project.


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