A284439 - OEIS

%I #14 Dec 29 2018 03:27:28

%S 1,91,8,2,61,11,5,6,4,62,3,31,32,41,12,111,21,92,121,13,14,7,51,15,9,

%T 16,71,17,33,611,18,81,19,22,82,112,83,113,42,34,63,72,35,43,73,36,

%U 114,64,65,211,212,115,116,44,66,45,37,117,38,23,621,131,122,631,118,24,641,123,52,119,25,511,213,141,132,133,124

%N Sum the last digit of a(n) and the first digit of a(n+1); keep only the leftmost digit of the result. The succession of those "leftmost digits" is the succession of the digits of the sequence itself.

%C The sequence is started with a(1) a= 1 and always extended with the smallest integer not yet present and not leading to a contradiction. There are no "0" digits in the sequence as a this 0 would be the leftmost digit of a later sum -- which is impossible.

%C Is this a permutation of the list (A052382) of numbers with no zero digits? - _N. J. A. Sloane_, Mar 27 2017

%H Jean-Marc Falcoz, <a href="/A284439/b284439.txt">Table of n, a(n) for n = 1..10001</a>

%e The 1st sum is 1+9, with result 10, and leftmost digit 1;

%e The 2nd sum is 1+8, with result 9, and leftmost digit 9;

%e The 3rd sum is 8+2, with result 10, and leftmost digit 1;

%e The 4th sum is 2+6, with result 8, and leftmost digit 8;

%e The 5th sum is 1+1, with result 2, and leftmost digit 2;

%e The 6th sum is 1+5, with result 6, and leftmost digit 6, etc.

%e The 6 "leftmost digits" so far are [1,9,1,8,2,6]; those are precisely the first 6 digits of the sequence.

%Y Cf. A052382.

%K nonn,base

%O 1,2

%A _Eric Angelini_ and _Jean-Marc Falcoz_, Mar 27 2017