Thursday, December 23, 2004

Prime multiplication table


Prime multiplication table to 1000 (or slightly over...)

7 11 13 17 19 23 29 31
7 49 - - - - - - -
11 77 121 - - - - - -
13 91 143 169 - - - - -
17 119 187 221 289 - - - -
19 133 209 247 323 361 - - -
23 161 253 299 391 437 529 - -
29 203 319 377 493 551 667 841 -
31 217 341 403 527 589 713 899 961
39 259 407 481 629 703 851 1073
41 287 451 533 697 779 943
43 301 473 559 731 817 989
47 329 517 611 799 893 1081
53 371 583 689 901 1007
59 413 649 767 1003
61 427 671 793
67 469 737 871
71 497 781 923
73 511 803 949
79 553 869 1027
83 581 913
89 623 979
97 679 1067
101 707 1111
103 721
107 749
109 763
113 791
127 889
131 917
137 959
139 973
149  1043
151  1057

Any three-digit number not divisible by 2, 3, or 5
must either be one of the above numbers, or it must be

343 = 7 × 7 × 7
539 = 7 × 7 × 11
637 = 7 × 7 × 13
833 = 7 × 7 × 17
931 = 7 × 7 × 19

...the next smallest combination is 7 × 11 × 13 = 1001.

Prime tableaux



Tableau encodings to 2100:

(ON bits are composite)

0000: 00.04.08.81.92.24.43

0210: 60.54.0D.87.30.A8.9A

0420: 48.86.98.CF.34.34.23

0630: 44.65.5A.A9.19.B6.42

0840: E1.87.9A.95.95.38.4A

1050: 4B.84.AB.CD.55.64.3A

1260: F0.06.3F.D5.7A.E0.8B

1470: 40.DD.68.99.90.37.A3

1680: E2.CD.2B.A3.5D.77.02

1890: D5.CE.7C.A1.32.EC.C2

[4-bit must be ON 8-bit must be ON 1-bit must be ON 2-bit must be ON]

Each tableau of length 30 is encoded by two decimal digits, where an on bit in each digit means that the associated number is composite:



First digit: 30n+1 30n+7 30n+11 30n+13
Second digit: 30n+17 30n+19 30n+23 30n+29


The colored digits above are characters where one of the bits is pre-determined due to a multiple of 7