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  There are 1307 XYYXF composites from C150 to C321 by this time. Currently 6 of them are reserved; the remaining 1301 are available for your choice.

This chart arranges the composites on (x; y) plane and shows their distribution by x and by y:

Blinking squares mark reserved composites. The color depends on the decimal length of the composite; that's shown on this chart representing the distribution of the composites by their decimal length:

You see, there's a lot of work to do. It would be fine if you choose some of these squares and cause me to add a few lines to the table below.


Reserved composites
Composite
Contributor
When reserved
C161_124_57
Sean Wellman
May 7, 2012
C217_134_64
Sean A. Irvine
April 30, 2012
C161_115_86
Sean Wellman
April 14, 2012
C151_111_95
Sean Wellman
April 6, 2012
C174_109_92
Sean Wellman
March 23, 2012
C261_149_145
Sean Wellman
February 17, 2012

To choose the most efficient method of factorization and to avoid wasting CPU time, please take into account that all the composites passed P±1 tests with B1 from 100M to 4G and ECM tests up to B1 = 11M, and now are being tested with ECM at B1 = 43M by yoyo@home.

Some of the numbers were tested with ECM a bit further; this table shows the amount of additional ECM tests.

Additional ECM work

Composites
B1
# of cycles
C187_107_97
110M
18000
C170_108_101
110M
18000
C194_108_103
110M
18000
C204_109_91
110M
18000
C195_109_94
110M
18000
C178_109_95
110M
18000
C164_109_98
110M
18000
C166_109_102
110M
18000
C177_109_106
110M
18000
C185_110_93
110M
18000
C205_110_97
110M
18000
C191_111_101
110M
7686
C220_111_106
110M
6070
C200_111_110
110M
6706
C211_127_90
110M
6400
C305_142_139
850M
9000
C310_147_142
850M
9000
C311_148_133
850M
9000
C313_148_139
850M
9000
C316_149_132
850M
9000
C261_149_145 (reserved)
110M
695
C321_149_146
850M
9000
C304_150_149
850M
9000

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Andrey Kulsha, Belarus