A037486 Base 9 digits are, in order, the first n terms of the periodic sequence with initial period 1,2.

1, 11, 100, 902, 8119, 73073, 657658, 5918924, 53270317, 479432855, 4314895696, 38834061266, 349506551395, 3145558962557, 28310030663014, 254790275967128, 2293112483704153

Offset

1,2

Links

Table of n, a(n) for n=1..17.

Index entries for linear recurrences with constant coefficients, signature (9,1,-9).

Formula

a(n) = 9*a(n-1) + a(n-2) - 9*a(n-3).

G.f.: x*(1+2*x)/((1-9*x)*(1-x^2)). a(n) = (11*9^n+4*(-1)^n-15)/80. - Bruno Berselli, Jan 20 2011

Mathematica

Table[FromDigits[PadRight[{}, n, {1, 2}], 9], {n, 20}] (* or *) LinearRecurrence[ {9, 1, -9}, {1, 11, 100}, 20] (* Harvey P. Dale, Feb 15 2020 *)

Crossrefs

Sequence in context: A081906 A098296 A037542 * A103720 A322719 A127806

Adjacent sequences: A037483 A037484 A037485 * A037487 A037488 A037489

Keyword

nonn,base,easy

Author

Clark Kimberling

Status

approved