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A239085
The sequence S = a(1), a(2), ... is defined by a(1)=1, if d,e,f are consecutive digits then we do not have d < e > f, and S is always extended with the smallest integer not yet present in S.
0
1, 2, 3, 4, 5, 6, 7, 8, 9, 90, 11, 10, 12, 20, 13, 30, 14, 40, 15, 50, 16, 60, 17, 70, 18, 80, 19, 91, 22, 21, 23, 31, 24, 41, 25, 51, 26, 61, 27, 71, 28, 81, 29, 92, 33, 32, 34, 42, 35, 52, 36, 62, 37, 72, 38, 82, 39, 93, 44, 43, 45, 53, 46, 63, 47, 73, 48, 83, 49, 94, 55, 54, 56, 64, 57, 74, 58, 84, 59, 95, 66, 65, 67, 75, 68, 85, 69, 96, 77, 76
OFFSET
1,2
COMMENTS
Computed by Lars Blomberg.
REFERENCES
Eric Angelini, Posting to Sequence Fans Mailing List, Sep 28 2013
LINKS
Eric Angelini, Less than <, Equal to =, Greater than > (see sequence Sc)
Eric Angelini, Less than <, Equal to =, Greater than > [Cached copy, with permission of the author]
MATHEMATICA
a[1]=1; a[n_]:=a[n]=Block[{k=1}, While[MemberQ[s=Array[a, n-1], k]||Or@@(#<#2>#3&@@@Partition[Flatten[IntegerDigits/@Join[s[[-2;; ]], {k}]], 3, 1]), k++]; k]; Array[a, 90] (* Giorgos Kalogeropoulos, May 14 2022 *)
CROSSREFS
The sequences in this family are given in A239083-A239086, A239136-A239139, A239087-A239090, A239215-A239218, A239235.
Sequence in context: A208130 A160343 A250265 * A273478 A278944 A303171
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Mar 10 2014
STATUS
approved