A075859 a(n) = n concatenated with n 1's and n.

111, 2112, 31113, 411114, 5111115, 61111116, 711111117, 8111111118, 91111111119, 10111111111110, 111111111111111, 1211111111111112, 13111111111111113, 141111111111111114, 1511111111111111115, 16111111111111111116, 171111111111111111117, 1811111111111111111118

Offset

1,1

Comments

All terms are divisible by 3. - Donald Sampson (marsquo(AT)hotmail.com), Dec 09 2003

References

J. Earls, On Smarandache Repunit N Numbers, Smarandache Notions Journal (2004), Vol. 14.1, pp 251-258.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..994

Formula

a(n) = n * 10^(n+L) + 10^L * R + n, where R is the n-th repunit and L is the number of decimal digits of n.

Mathematica

Array[FromDigits@ Join[#1, #2, #1] & @@ {IntegerDigits[#], ConstantArray[1, #]} &, 16] (* Michael De Vlieger, Mar 21 2018 *)
Table[10^IntegerLength[n] (n*10^n+FromDigits[PadRight[{}, n, 1]])+n, {n, 20}] (* Harvey P. Dale, May 04 2026 *)

Crossrefs

Cf. A075842, A075858.

Sequence in context: A137465 A101152 A250145 * A264466 A302384 A303105

Adjacent sequences: A075856 A075857 A075858 * A075860 A075861 A075862

Keyword

base,easy,nonn,less

Author

Jason Earls, Oct 15 2002

Extensions

More terms from Donald Sampson (marsquo(AT)hotmail.com), Dec 09 2003

Status

approved