A328991 a(n) = concatenation of a(n-1),2,a(n-2),2,a(n-1), with a(1)=1, a(2)=1221.

1, 1221, 12212121221, 1221212122121221212212121221, 122121212212122121221212122121221212122121221212122121221212212121221

Offset

1,2

Comments

In the Allombert et al. (2018) paper the sequence starts with a(0) = the empty string.

References

Allombert, Bill, Nicolas Brisebarre, and Alain Lasjaunias. "On a two-valued sequence and related continued fractions in power series fields." The Ramanujan Journal 45.3 (2018): 859-871. See W_n in Theorem 2.

Links

Table of n, a(n) for n=1..5.

Crossrefs

Sequence in context: A091790 A053655 A068262 * A223118 A128655 A251446

Adjacent sequences: A328988 A328989 A328990 * A328992 A328993 A328994

Keyword

nonn

Author

N. J. A. Sloane, Nov 09 2019

Status

approved