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

Author

Amarnath Murthy, Aug 22 2005

Keywords

• base
• easy
• nonn

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

Examples

			a(90) = 9009.
		

Links

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

Crossrefs

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

Programs

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

Extensions

More terms from Joshua Zucker, May 08 2006

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