A291092 1 followed by infinitely many 9's.

1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9

Offset

1,2

Comments

The digital root of 9^(n-1). - Cino Hilliard, Dec 31 2004

With interpolated zeros (1,0,9,0,9,0,9,0,...) this is the number of hours between times when the hands of a two-handed clock cross. - Halfdan Skjerning, Aug 18 2017

Links

Table of n, a(n) for n=1..87.

Brady Haran and Cliff Stoll, When do clock hands overlap?, Numberphile video (2017)

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

Formula

G.f.: x*(1 + 8*x)/(1 - x). - Chai Wah Wu, Aug 19 2017

E.g.f.: 9*(exp(x) - 1) - 8*x. - Stefano Spezia, Oct 16 2023

Mathematica

PadRight[{1}, 100, 9] (* Paolo Xausa, Oct 16 2023 *)

Crossrefs

Cf. A178181, A010734, A180599, A100403, A100401.

Sequence in context: A181693 A271880 A180599 * A010734 A066568 A291514

Adjacent sequences: A291089 A291090 A291091 * A291093 A291094 A291095

Keyword

nonn,easy

Author

N. J. A. Sloane, Aug 19 2017

Status

approved