A244842 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A244842

a(n) = (10^n - 1)*(10^n - 10)/90.

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, A109242.

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