A111708 a(n) = n concatenated with 9's complement of n.

9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 1089, 1188, 1287, 1386, 1485, 1584, 1683, 1782, 1881, 1980, 2079, 2178, 2277, 2376, 2475, 2574, 2673, 2772, 2871, 2970, 3069, 3168, 3267, 3366, 3465, 3564, 3663, 3762, 3861, 3960, 4059, 4158, 4257, 4356, 4455, 4554

Offset

0,1

Comments

If n has k digits a(n) is a multiple of 10^k -1.

The sequence contains 10^(k) multiples of 10^k -1.

a(n)/{10^k -1} gives all natural numbers.

All terms are multiples of 9: A007953(a(n))=9*A055642(n); A010888(a(n))=9. - Reinhard Zumkeller, Sep 17 2015

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..9999

Example

a(90) = 9009.

Prog

(Haskell)
a111708 0 = 9
a111708 n = f [] n where
   f ys 0 = foldl (\v d -> 10 * v + d) 0 $ ys ++ map (9 -) ys
   f ys x = f (d : ys) x' where (x', d) = divMod x 10
-- Reinhard Zumkeller, Sep 17 2015

Crossrefs

Cf. A061601, A010888, A007953, A055642, subsequence of A262277.

Sequence in context: A070793 A052223 A085132 * A248050 A044052 A131418

Adjacent sequences: A111705 A111706 A111707 * A111709 A111710 A111711

Keyword

base,easy,nonn

Author

Amarnath Murthy, Aug 22 2005

Extensions

More terms from Joshua Zucker, May 08 2006

Definition cleared and offset changed by Reinhard Zumkeller, Sep 17 2015

Status

approved