A037543 Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 1,2,1.

1, 12, 121, 1211, 12112, 121121, 1211211, 12112112, 121121121, 1211211211, 12112112112, 121121121121, 1211211211211, 12112112112112, 121121121121121, 1211211211211211

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• easy

Links

• Index entries for linear recurrences with constant coefficients, signature (10,0,1,-10).

Programs

PARI

Vec(x*(1+x)^2/((x-1)*(10*x-1)*(1+x+x^2)) + O(x^25)) \\ Jinyuan Wang, Apr 14 2020

Formula

G.f.: x*(1+x)^2 / ( (x-1)*(10*x-1)*(1+x+x^2) ). - R. J. Mathar, Aug 12 2013