A180599 - OEIS

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A180599

Zero followed by infinitely many 9's.

0, 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

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OFFSET

0,2

COMMENTS

Another interpretation: A real number with an infinitesimally small difference from the integer 1 which is used to test the precision of calculating devices. - John W. Nicholson, Feb 01 2012

a(n) is also the number of n-digit positive repdigit numbers (A010785). - Stefano Spezia, Aug 15 2020

LINKS

Table of n, a(n) for n=0..86.

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

FORMULA

a(0) = 0, a(n) = 9 for n > 0.

a(n) = 9 * A057427(n).

a(n) = A010888(9*n), where A010888 is the digital root.

From Robert Israel, Dec 16 2014: (Start)

G.f.: 9*x/(1 - x).

E.g.f.: 9*(exp(x) - 1). (End)

EXAMPLE