A025143 Unique sequence a of 1's and 2's such that a(1) = 2 and r(r(a)) = a != r(a), where for any sequence s, r(s) is the sequence of lengths of runs of same symbols in s; r(a) is sequence A025142.

2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 2, 1, 1, 2, 1, 2

Offset

1,1

References

C. Kimberling, Problem 90: Run-length sequences, Mathematische Semesterberichte, 44 (1997) 94-95.

Links

Table of n, a(n) for n=1..111.

Crossrefs

Cf. A025142.

Differs from A014675 in many entries starting at entry 8.

Cf. A078880 (satisfies s = r(s)), A288724 (satisfies s = r(r(r(s)))).

Sequence in context: A100429 A049710 A352632 * A174314 A237253 A080634

Adjacent sequences: A025140 A025141 A025142 * A025144 A025145 A025146

Keyword

nonn

Author

Clark Kimberling

Status

approved