A335493 - OEIS

%I #18 Sep 05 2021 01:17:17

%S 0,1,2,3,4,5,6,7,8,9,17,23,28,29,30,36,42,49,55,58,61,64,66,68,70,75,

%T 79,79,79,82,84,89,94,96,98,98,98,100,101,108,115,117,119,121,123,125,

%U 127,129,130,136,142,146,150,151,151,156,161,164,167,168,169,170,171,172,179,180,180,181,182,183,183

%N The successive absolute differences between two digits are the successive differences between two terms. See in the Comments section why a(n) = a(n-1) sometimes.

%C To extend the sequence S with a new term a(n), we always add to a(n-1) the last absolute difference D between two digits that must be considered. As a term of S can have two successive identical digits [like a(19) = 55 here], or, in general, as two successive digits of S can be identical, we will see sometimes in S two or more equal terms following each other [like a(27) = a(28) = a(29) = 73 here].

%H Carole Dubois, <a href="/A335493/b335493.txt">Table of n, a(n) for n = 1..5002</a>

%e After a(10) = 9, we cannot extend S with a(11) < 17 as the difference between a(10) and a(11) cannot be < 8, this 8 being the difference between 9 and the first digit of a(11);

%e After a(11) = 17, we are driven by the next absolute difference between digits, which is 6 (the difference between the 1 and the 7 of 17). We add this 6 to a(11) = 17 to get a(12) = 23; etc.

%e We have seen in the Comments section why we sometimes have to add 0 to a(n), which leads to a(n+1) = a(n).

%Y Cf. A335492 [same idea but a(n) is sometimes < a(n-1)].

%K base,nonn

%O 1,3

%A _Eric Angelini_ and _Carole Dubois_, Jun 11 2020