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A102484 Numbers of the concatenated form 9nn9. 5
9009, 9119, 9229, 9339, 9449, 9559, 9669, 9779, 9889, 9999, 910109, 911119, 912129, 913139, 914149, 915159, 916169, 917179, 918189, 919199, 920209, 921219, 922229, 923239, 924249, 925259, 926269, 927279, 928289, 929299, 930309 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = 9*(1 + 10^(2*A055642(n-1)+1))+(n-1)*(10+10^(1+A055642(n-1))). - Robert Israel, May 09 2017

EXAMPLE

For n=0 we concatenate 3, 0, 0 and 3 to get 3003.

For n=10 we concatenate 3, 10, 10 and 3 to get 310103.

MAPLE

f:= n -> 9 + 9*10^(2*ilog10(n-1)+3)+(n-1)*(10+10^(2+ilog10(n-1))):

f(1):= 9009;

map(f, [$1..200]); # Robert Israel, May 09 2017

MATHEMATICA

With[{k = {9}}, Table[FromDigits@ Join[k, #, #, k] &@ IntegerDigits[n], {n, 0, 30}]] (* Michael De Vlieger, May 09 2017 *)

CROSSREFS

Cf. A100846 for 1nn1; A100896 for 3nn3; A100897 for 7nn7.

Cf. A055642.

Sequence in context: A202531 A106770 A326319 * A295457 A252456 A196994

Adjacent sequences:  A102481 A102482 A102483 * A102485 A102486 A102487

KEYWORD

easy,nonn,base

AUTHOR

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 12 2005

STATUS

approved

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Last modified June 1 11:05 EDT 2020. Contains 334762 sequences. (Running on oeis4.)