**Size in cells:**
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
Larger

**Cost in gliders:**
4 |
5 |
6 |
1 glider/bit |
>1 glider/bit |
unknown

Block on beacon [4] |

Up boat on beacon [4] | Down boat on beacon [6] |

Due to space limitations, these and their syntheses are shown on a separate page.

Due to space limitations, these and their syntheses are shown on a separate page.

Due to space limitations, these are shown without syntheses on a separate page. All of these can be synthesized using the same techniques that are used for smaller pseudo-oscillators and pseudo-still-lifes. Syntheses for 14 of them are shown here.

Due to space limitations, these are shown without syntheses on a separate page. All of these can be synthesized using the same techniques that are used for smaller pseudo-oscillators and pseudo-still-lifes, except 4 that involve adding a block to 15-bit period 2 oscillators with no known syntheses. These and ten other syntheses are shown here.

Due to space limitations, these are shown without syntheses on a separate page.

All of these can be synthesized using the same techniques that are used for smaller pseudo-oscillators and pseudo-still-lifes, except 25 trivial ones that involve adding a small simple still-life to a large complex period 2 oscillator that does not yet have a synthesis (i.e. 8 with a boat on one of three 15-bit oscillators, and 17 with a block on one of ten 16-bit oscillators). These are not included in the list below.

Due to space limitations, these are shown without syntheses on a separate page.

All of these can be synthesized using the same techniques that are used for smaller pseudo-oscillators and pseudo-still-lifes, except one non-trivial one (shown below) and 169 trivial ones (not shown below) that involve adding a small still-life or oscillator to a large complex period 2 oscillator that does not yet have a synthesis:

- 36 with 6-bit still-life one of three 15-bit period 2 oscillators.
- 16 with beacon on one of three 15-bit period 2 oscillators.
- 33 with boat on of ten 16-bit period 2 oscillators.
- 84 with block on one of 21 17-bit period 2 oscillators.

Here are syntheses (or lack thereof) for 11 of these. All of the expensive ones were once on the "non-trivial without synthesis" list for a long time, but were eventually solved. Note that these, plus the ones without syntheses, all share three mechanisms that are all very difficult to synthesize: a beacon sandwiched between two other pieces, a bipole with pieces wrapped around it, or a cis python whose free end is near something else.

Boat on beehive on griddle [11] | Down tripole on long cis integral [20] |

Tripole below paper clip [10] | Beacon between gull w/ two very long hooks [137] |

Cis cis quad-beacon [8] |

Two blocks on spark coil [6] | Two beacons on two eaters [10] |

Block on beacon [4] | Up boat on beacon [4] | Cis block on beacon on block [4] |

All period 2 pseudo-oscillators up to 17 bits have been synthesized. All period 2 pseudo-oscillators up to 21 bits can be synthesized using the same techniques used for smaller pseudo-oscillators and pseudo-still-lifes, except one non-trivial one, and many trivial ones.

There are many trivial pseudo-objects, consisting of a small objects added to a large object that, itself, has eluded synthesis. These include:

- 4 19-bit pseudo-objects (shown) from a block on one of the three unbuildable 15-bit period 2 oscillators.
- 25 20-bit pseudo-objects (not shown), 8 from a boat on one of the three unbuildable 15-bit period 2 oscillators, and 17 from a block on one of ten unbuildable 16-bit period 2 oscillators.
- 169 21-bit pseudo-objects (not shown), 52 from a beacon or six-bit still-life on one of the three unbuildable 15-bit period 2 oscillators, 33 from a boat on one of ten unbuildable 16-bit period 2 oscillators, and 84 from a block on one of 21 unbuildable 17-bit period 2 oscillators.

The 4 trivial 19-bit ones, and the 1 non-trivial 21-bit ones shown here. (The 25 trivial 20-bit ones and 169 trivial 21-bit ones above are not shown.)

Block on 15-bit P2 #1 [x+2] | Block on blinkers bit pole [x+2] | Block on 15-bit P2 #5 [x+2] | Block below 15-bit P2 #5 [x+3] | Up snake on up beacon above long hook w/ tail [x] |

**Related:**
period-2 oscillators.

**Other
pseudo-oscillators by period:**
2,
3,
4,
5,
6,
8,
10,
12,
15,
30,
60,
other.

**Other types:**
still-lifes,
pseudo-still-lifes,
oscillators,
pseudo-oscillators,
oscillators by period,
pseudo-oscillators by period,
guns,
multi-colored Life,
basic spaceships and pseudo-spaceships,
exotic spaceships,
spaceships flotillae,
puffers,
constellations,
methuselahs,
not quite stable objects.

**See also:** Life objects sorted by:
counts,
frequency of occurrence,
cost in gliders,
name,
size in bits,
or type.

Copyright © 1997, 1998, 1999, 2013, 2014 by Mark. D. Niemiec.
All rights reserved.

This page was last updated on
*2015-02-19*.