A179956 a(n) is the smallest integer that contains a(n-1) but does not begin with a(n-1).

1, 21, 121, 1121, 11121, 111121, 1111121, 11111121, 111111121, 1111111121, 11111111121, 111111111121, 1111111111121, 11111111111121, 111111111111121, 1111111111111121, 11111111111111121, 111111111111111121, 1111111111111111121, 11111111111111111121

Offset

1,2

Links

Table of n, a(n) for n=1..20.

Formula

For n > 2, a(n) = 10^(n-1) + a(n-1). - Jon Maiga, Aug 04 2019

Example

The next term after 1 is 21, because 21 is the lowest integer higher than 1 that contains a 1 but does not start with 1.

Mathematica

a[1] = 1
a[2] = 21
a[n_] := 10^(n - 1) + a[n - 1]
Array[a, 20] (* Jon Maiga, Aug 04 2019 *)

Crossrefs

Sequence in context: A200888 A179441 A164785 * A117388 A053052 A243882

Adjacent sequences: A179953 A179954 A179955 * A179957 A179958 A179959

Keyword

easy,base,nonn

Author

Dominick Cancilla, Aug 03 2010

Extensions

Definition corrected and more terms added by Jon Maiga, Aug 04 2019

Status

approved