A300907 a(n) is the least positive integer not yet in the sequence in which the largest digit of a(n-2) appears among its digits; a(1)=1, a(2)=2.
1, 2, 10, 12, 11, 20, 13, 21, 3, 22, 23, 24, 30, 4, 31, 14, 32, 34, 33, 40, 35, 41, 5, 42, 15, 43, 25, 44, 45, 46, 50, 6, 51, 16, 52, 26, 53, 36, 54, 56, 55, 60, 57, 61, 7, 62, 17, 63, 27, 64, 37, 65, 47, 66, 67, 68, 70, 8, 71, 18, 72, 28, 73, 38, 74, 48, 75, 58, 76, 78, 77, 80
Offset: 1
Examples
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
Crossrefs
Cf. A286890.
Programs
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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 *)
Comments