

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").


0



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
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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



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, n1]][[n]]MemberQ[Array[a, n1], k], k++]; k]; Array[a, 72] (* Giorgos Kalogeropoulos, May 12 2023 *)


CROSSREFS



KEYWORD

base,nonn


AUTHOR



STATUS

approved



