A095752 a(n) = (1/9)*(-1+10^n)*(4*n+3).

7, 121, 1665, 21109, 255553, 2999997, 34444441, 388888885, 4333333329, 47777777773, 522222222217, 5666666666661, 61111111111105, 655555555555549, 6999999999999993, 74444444444444437, 788888888888888881

Offset

1,1

Comments

Numbers with increasingly larger and larger one-digit centers.

References

Discovered by Jason Earls.

Links

Table of n, a(n) for n=1..17.

Formula

O.g.f.: -x*(2*x+7)*(5*x-1)/[(-1+x)^2*(-1+10*x)^2]. - R. J. Mathar, Feb 26 2008

Mathematica

Table[(10^n-1) (4n+3)/9, {n, 20}] (* Harvey P. Dale, Jun 29 2026 *)

Crossrefs

Sequence in context: A197041 A283625 A372615 * A113267 A274267 A012028

Adjacent sequences: A095749 A095750 A095751 * A095753 A095754 A095755

Keyword

easy,nonn,changed

Author

Michael Joseph Halm, Jul 10 2004

Status

approved