A239217 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.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 30, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 40, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 50, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 60, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 70, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 80, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 90, 89, 91, 92, 93, 94, 95, 96, 97, 98, 99, 101, 102, 103, 104, 105, 106, 107, 108, 109

Offset: 1

Author

Michel Marcus and N. J. A. Sloane, Mar 12 2014

Keywords

• nonn
• base

Comments

Computed by Lars Blomberg.

More than the usual number of terms are displayed, in order to show the difference from A130571. Differs from A130571 at index 91: a(91) = 91, while A130571(91) = 100.

References

• Eric Angelini, Posting to Sequence Fans Mailing List, Sep 28 2013.

Links

• Eric Angelini, Less than <, Equal to =, Greater than > (see sequence St)
• Eric Angelini, Less than <, Equal to =, Greater than > [Cached copy, with permission of the author]

Crossrefs

The sequences in this family are given in A239083-A239086, A239136-A239139, A239087-A239090, A239215-A239218, A239235.

Cf. A130571.

Programs

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[Last@s,{k}]],3,1]),k++];k];Array[a,108] (* Giorgos Kalogeropoulos, May 13 2022 *)