[seqfan] An "add or make the absolute difference" array
Eric Angelini
Eric.Angelini at kntv.be
Wed Feb 15 15:22:38 CET 2012
Hello SeqFans,
could someone check and extend this seq (if of interest)?
[Requires lots of memory]
S = 1, 2, 4, 7, 8, 10, 13, 12, 16, 20, 19, ...
The idea:
- to put all the Naturals in an array, exactly once.
The array rule:
- if you take 2 neighboring integers anywhere in the array,
their sum or their absolute difference is on the line below,
between them.
The construction:
- Start the uppermost row with "1"
- extend the uppermost row with the "smallest integer not yet
present in the array and not leading to a contradiction",
checking first if the absolute difference between the new
integer and its left neighbor is not yet present in the array
-- else checking if the new integer can be added to its left
neighbor with no subsequent "damage" either (the result --
subtraction or addition -- will be written on the line below,
between the two integers, starting an anti-diagonal)
- complete the said anti-diagonal in the same way, then extend
the uppermost row with a new integer.
1 2 4 7 8 10 13 12 16 20 19
3 6 11 15 18 23 25 28 36 39
9 5 26 33 41 48 53 64 75
14 21 59 74 89 101 117 139
35 38 133 163 190 218 256
73 95 30 353 408 474
22 65 323 55 66
43 258 268 121
215 526 147
Best, 311 379
É. 68
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