[seqfan] Re: Absolute first differences of S are the terms in even position in S itself

[Eric Angelini]

A new link and sequence, thanks to the sound remarks of
Maximilian Hasler (off list):
http://www.cetteadressecomportecinquantesignes.com/FirstDiffEven.htm
Sorry to post twice today (blame it on the snow)!
Best,
É.
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          S = 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,...
Even pos. E = . 1 . 2 . 1 . 3 . 4 .  5 .  3 .  6 .  5 .  7 .  6 .  8 .  10
First dif D =  1 2 1 3 4 5 3 6 5 7  6 8 10 ... --> this forms E again