A362987 Lexicographically earliest sequence S of distinct positive terms such that the successive digits of S are the successive spreads of S' terms (see Comments for definition of "spread").

10, 11, 12, 21, 23, 13, 20, 32, 24, 14, 34, 25, 31, 22, 30, 35, 42, 15, 43, 26, 36, 37, 46, 16, 41, 45, 53, 57, 47, 33, 52, 27, 40, 64, 54, 38, 48, 58, 68, 17, 63, 28, 69, 18, 51, 39, 56, 60, 59, 65, 62, 49, 50, 74, 61, 29, 73, 70, 85, 96, 72, 75, 79, 81, 84, 44, 71, 95, 83, 105, 104, 19

Offset

1,1

Comments

The spread of n is the absolute difference between the leftmost digit of n and the rightmost digit of n. Spreads vary from 0 to 9.

Links

Table of n, a(n) for n=1..72.

Example

a(1) = 10 with spread 1;
a(2) = 11 with spread 0;
a(3) = 12 with spread 1;
a(4) = 21 with spread 1;
a(5) = 23 with spread 1;
a(6) = 13 with spread 2; etc.
We see that the above succession of spreads is the digits' succession of S.

Mathematica

a[1]=10; a[n_]:=a[n]=Block[{k=10}, While[Abs[First@#-Last@#]&@IntegerDigits[k][[{1, -1}]]!=Flatten[IntegerDigits/@Array[a, n-1]][[n]]||MemberQ[Array[a, n-1], k], k++]; k]; Array[a, 72] (* Giorgos Kalogeropoulos, May 12 2023 *)

Crossrefs

Cf. A100787.

Sequence in context: A207671 A154328 A112654 * A235828 A102695 A376314

Adjacent sequences: A362984 A362985 A362986 * A362988 A362989 A362990

Keyword

base,nonn

Author

Eric Angelini, May 12 2023

Status

approved