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A070252 Number of n-digit palindromes. 7
10, 9, 90, 90, 900, 900, 9000, 9000, 90000, 90000, 900000, 900000, 9000000, 9000000, 90000000, 90000000, 900000000, 900000000, 9000000000, 9000000000, 90000000000, 90000000000, 900000000000, 900000000000, 9000000000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..25.

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

FORMULA

From Colin Barker, Aug 19 2013: (Start)

a(n) = 10*a(n-2) for n>3.

G.f.: x*(10*x^2-9*x-10) / (10*x^2-1). (End)

E.g.f.: x + 9*(cosh(sqrt(10)*x) - 1 + sqrt(10)*sinh(sqrt(10)*x))/10. - Stefano Spezia, Jun 11 2022

MATHEMATICA

LinearRecurrence[{0, 10}, {10, 9, 90}, 25] (* Stefano Spezia, Jun 11 2022 *)

CROSSREFS

A variant of A050683, which is the principal entry for this sequence. Cf. A016115.

Partial sums give A070199.

Sequence in context: A241285 A052196 A243035 * A038311 A244960 A282560

Adjacent sequences: A070249 A070250 A070251 * A070253 A070254 A070255

KEYWORD

base,nonn,easy

AUTHOR

Amarnath Murthy, May 06 2002

STATUS

approved

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Last modified February 2 12:13 EST 2023. Contains 360011 sequences. (Running on oeis4.)