OFFSET
1,2
COMMENTS
Starting from the term a(89)=89, every term must contain a 9.
EXAMPLE
For n=5, a(n-2) = 10 which has largest digit 1. The positive integers containing 1 are 1, 10, 11, 12, 13, ... (A011531). Since 1 and 10 are already in the sequence, a(5) = 11. - Michael B. Porter, Mar 17 2018
MATHEMATICA
FromDigits /@ Nest[Function[a, Append[a, Block[{k = 3, d}, While[Nand[FreeQ[a, #], MemberQ[#, Max@ a[[-2]]]] &@ Set[d, IntegerDigits@ k], k++]; d]]], {{1}, {2}}, 70] (* Michael De Vlieger, Mar 16 2018 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Enrique Navarrete, Mar 14 2018
STATUS
approved