A287205 - OEIS

A287205

Starting with a(1)=1 and excluding the digit 0 in any term in the sequence, a(n)=smallest nonnegative integer not yet in the sequence such that a(n-1) and a(n) altogether have exactly one consecutive digit for at most one digit.

1, 12, 2, 11, 3, 22, 4, 33, 5, 44, 6, 55, 7, 66, 8, 77, 9, 88, 13, 31, 14, 41, 15, 51, 16, 61, 17, 71, 18, 81, 19, 91, 99, 121, 123, 32, 21, 124, 42, 23, 34, 43, 35, 52, 24, 45, 53, 36, 62, 25, 54, 46, 63, 37, 72, 26, 64, 47, 73, 38, 82, 27, 74, 48, 83, 39, 92, 28, 84, 49, 93, 112, 29, 94, 113

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OFFSET

1,2

COMMENTS

Note that upon removing commas, strings such as 111 and 1122 are not allowed. That is why 111 is not in the sequence and 99 is not followed by 112. The digit 0 is also not allowed as defined in the name.

LINKS

Table of n, a(n) for n=1..75.

MATHEMATICA

a = {{1}}; Do[k = 1; While[Nand[! MemberQ[a, #], Count[Length /@ Split[a[[n - 1]]~Join~#], 2] == 1, ! MemberQ[#, 0]] &@ Set[d, IntegerDigits@ k], k++]; AppendTo[a, d], {n, 2, 74}]; FromDigits /@ a (* Michael De Vlieger, May 22 2017 *)

CROSSREFS

Cf. A283430.

Sequence in context: A099136 A215416 A264970 * A183729 A238718 A303782

Adjacent sequences: A287202 A287203 A287204 * A287206 A287207 A287208

KEYWORD

nonn,base

AUTHOR

Enrique Navarrete, May 21 2017

STATUS

approved