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

Author

N. J. A. Sloane, Aug 19 2017

Keywords

• nonn
• easy

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

• Brady Haran and Cliff Stoll, When do clock hands overlap?, Numberphile video (2017)
• Index entries for linear recurrences with constant coefficients, signature (1).

Crossrefs

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

Programs

Mathematica

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

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