A110740 Numbers k such that the concatenation 1,2,3,...,(k-1) is divisible by k.

1, 3, 9, 27, 69, 1053, 1599, 2511, 8167, 21371, 73323, 225681, 313401, 362703, 371321, 1896939, 2735667, 3426273, 3795093, 5433153, 302278903, 1371292077, 19755637749, 23560349643

Offset

1,2

Comments

Subsequence of A029455 composed of the terms coprime to 10. - Max Alekseyev, Jun 07 2023

Links

Table of n, a(n) for n=1..24.

Example

3 divides 12, 9 divides 12345678.

Mathematica

s = ""; Do[s = s <> ToString[n]; If[Mod[ToExpression[s], n + 1] == 0, Print[n + 1]], {n, 0, 5*10^6}] (* Ryan Propper, Aug 28 2005 *)
Select[Range[55*10^5], Divisible[FromDigits[Flatten[IntegerDigits/@Range[ #-1]]], #]&] (* Harvey P. Dale, Mar 28 2020 *)

Crossrefs

Cf. A007908, A029455, A094151, A171785, A332580, A362966.

Sequence in context: A191007 A036215 A103828 * A348555 A042938 A206604

Adjacent sequences: A110737 A110738 A110739 * A110741 A110742 A110743

Keyword

base,nonn,more

Author

Amarnath Murthy, Aug 10 2005

Extensions

More terms from Ryan Propper, Aug 28 2005

a(20) from Giovanni Resta, Apr 10 2018

a(21)-a(24) from Scott R. Shannon, using a modified version of an algorithm by Joseph Myers, Apr 10 2020

Status

approved