A110430 Arithmetic mean of all n-digit positive even numbers.

5, 54, 549, 5499, 54999, 549999, 5499999, 54999999, 549999999, 5499999999, 54999999999, 549999999999, 5499999999999, 54999999999999, 549999999999999, 5499999999999999, 54999999999999999, 549999999999999999, 5499999999999999999

Offset

0,1

Links

Table of n, a(n) for n=0..18.

Formula

a(n) =1/2{10^(n-1) + 10^n -2}

Example

a(2) = Arithmetic mean of 10,12,14,...96,98 =(10 + 98)/2 =54.

Mathematica

Table[FromDigits[PadRight[{5, 4}, n, 9]], {n, 20}] (* Harvey P. Dale, Apr 24 2020 *)

Crossrefs

Sequence in context: A268882 A229298 A087125 * A110432 A215542 A304322

Adjacent sequences: A110427 A110428 A110429 * A110431 A110432 A110433

Keyword

base,easy,nonn

Author

Amarnath Murthy, Aug 02 2005

Extensions

Corrected and extended by Joshua Zucker, May 10 2006

Status

approved