[seqfan] The a(n)th digit of U is the 2nd digit following a(n)

Eric Angelini Eric.Angelini at kntv.be
Sat Sep 27 21:14:50 CEST 2014

Hello SeqFans,
Here is again a permutation of the integers > 0.
I like it a lot as the sequence smoothly 
builds itself quite easily.

U is the lexico-first with the property
that the a(n)th digit of S is the second 
digit following a(n) in the sequence.


12 says that the 12th digit of U is a 4
(indeed, it is the 4 in 43)
3 says that the 3rd digit of U is a 1
(indeed, it is the 1 in 12)
27 (look at the present end of U) says
that the 27th digit of U is 5
(indeed, it is the 5 in 15)
Always extend U with the smallest
available integer not yet used and 
not leading to a contradiction.

U is infinite and shows once every
integer from 1 to oo.

I'm sure someone will find a typo 
somewhere -- please forgive me in

I'd love to see the graph of U -- any

Catapulté de mon aPhone

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