Weird Stuff
Contributed by Anthony Chen.
1 + 2 + 1 = 22
1 + 2 + 3 + 2 +1 = 32
1 + 2 + 3 + 4 + 3 + 2 + 1 = 42
etc.
1 + 3 = 22
1 + 3 + 5 = 32
1 + 3 + 5 + 7 = 42
1 + 3 + 5 + 7 + 9 = 52
etc.
142,857 * 2-6 = {1,4,2,8,5,7} rearranged
14 + 28 + 57 = 99
142 + 857 = 999
12 = 1
112 = 121
1112 = 12321
11112 = 1234321
etc.
342 = 1156
3342 = 111556
33342 = 11115556
333342 = 1111155556
etc.
672 = 4489
6672 = 444889
66672 = 44448889
666672 = 4444488889
etc
987654321...
... * 18 = 17,777,777,778
... * 27 = 26,666,666,667
... * 36 = 35,555,555,556
... * 45 = 44,444,444,445
... * 54 = 53,333,333,334
... * 63 = 62,222,222,223
... * 72 = 71,111,111,112
... * 81 = 80,000,000,001
Notice the multiplier of 987654321's first and last digit is the same as the product's.