[seqfan] Absolute first differences of S are the odd terms of S itself

[Eric Angelini]

Hello SeqFans,

          S = 1,2,1,3,2,5,1,6,3,9,4,11,5,13,3,12,6,17,5,18,7,21,6,22,8,25,10,...
Odd terms O = 1 . 1 . 2 . 1 . 3 . 4 .  5 .  3 .  6 .  5 .  7 .  6 .  8 .  10
First dif D =  1 1 2 1 3 4 5 3 6 5 7  6 8 10 ... --> this forms O again

We have decided here to "always take, when possible, the smallest available 
first difference not yet in D and not leading to a contradiction".

Best,
É.
(a bit more to read on this:
http://www.cetteadressecomportecinquantesignes.com/FirstDiffOdd.htm )