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A244842 a(n) = (10^n - 1)*(10^n - 10)/90. 1
0, 99, 10989, 1109889, 111098889, 11110988889, 1111109888889, 111111098888889, 11111110988888889, 1111111109888888889, 111111111098888888889, 11111111110988888888889, 1111111111109888888888889, 111111111111098888888888889, 11111111111110988888888888889 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For n > 1, the digit sums of a(n) are 18, 27, 36, ..., 9n (see example).

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..100

Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000).

FORMULA

G.f.: -99*x / ( (x-1)*(100*x-1)*(10*x-1) ). - R. J. Mathar, Jul 11 2014

a(n) = 99*A109242(n-2). - R. J. Mathar, Jul 11 2014

EXAMPLE

-------------------------------------------------------

n    a(n)                    digitsum(a(n))    9*n

-------------------------------------------------------

2:   99                            18          9*2

3:   10989                         27          9*3

4:   1109889                       36          9*4

5:   111098889                     45          9*5

6:   11110988889                   54          9*6

7:   1111109888889                 63          9*7

8:   111111098888889               72          9*8

9:   11111110988888889             81          9*9

10:  1111111109888888889           90         9*10

11:  111111111098888888889         99         9*11

12:  11111111110988888888889      108         9*12, etc.

MAPLE

A244842:=n->(10^n - 1)*(10^n - 10)/90: seq(A244842(n), n=1..15);

MATHEMATICA

Table[(10^n - 1) (10^n - 10)/90, {n, 15}]

PROG

(MAGMA) [(10^n-1)*(10^n-10)/90: n in [1..15]];

CROSSREFS

Cf. A053422.

Sequence in context: A098609 A195623 A274743 * A190921 A213694 A295434

Adjacent sequences:  A244839 A244840 A244841 * A244843 A244844 A244845

KEYWORD

nonn,easy

AUTHOR

Wesley Ivan Hurt, Jul 08 2014

STATUS

approved

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Last modified April 19 01:29 EDT 2019. Contains 322237 sequences. (Running on oeis4.)