A037519 Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 2,0,1.

2, 20, 201, 2012, 20120, 201201, 2012012, 20120120, 201201201, 2012012012, 20120120120, 201201201201, 2012012012012, 20120120120120, 201201201201201, 2012012012012012

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..100

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

Formula

G.f.: (x*(2+x^2)) / ((x-1)*(10*x-1)*(1+x+x^2)). - R. J. Mathar, Nov 21 2011

Mathematica

LinearRecurrence[{10, 0, 1, -10}, {2, 20, 201, 2012}, 40] (* Vincenzo Librandi, Nov 23 2011 *)
Table[FromDigits[PadRight[{}, n, {2, 0, 1}]], {n, 20}] (* Harvey P. Dale, Sep 18 2018 *)

Prog

(Magma) I:=[2, 20, 201, 2012]; [n le 4 select I[n] else 10*Self(n-1)+Self(n-3)-10*Self(n-4): n in [1..20]]; // Vincenzo Librandi, Nov 23 2011

Crossrefs

Sequence in context: A136902 A136884 A093136 * A037722 A109107 A037729

Adjacent sequences: A037516 A037517 A037518 * A037520 A037521 A037522

Keyword

nonn,base,easy

Author

Clark Kimberling

Status

approved