A029495 Numbers k such that k divides the (right) concatenation of all numbers <= k written in base 2 (most significant digit on right).

1, 5, 337

Offset: 1

Author

Olivier Gérard

Keywords

• nonn
• base
• bref
• more

Comments

This sequence differs from A061931 in that all least significant zeros are kept during concatenation.

No more terms < 10^7. - Lars Blomberg, Oct 01 2011

Examples

			12345 -> (1)(01)(11)(001)(101) base 2 -> 10111001101 base 2 = 1485 and 5 divides 1485.
		

Links

• Index entries for related sequences

Crossrefs

Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.

Programs

Mathematica

b = 2; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[c, Reverse[IntegerDigits[#, b]]], b], #] &] (* Robert Price, Mar 12 2020 *)

PARI

is(n) = my(t=[]); for(k=1, n, t=concat(t, Vecrev(binary(k)))); if(Mod(subst(Pol(t), x, 2), n)==0, return(1), return(0)) \\ Felix Fröhlich, Jul 06 2017

Extensions

Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002

Additional comments, more terms and example from Larry Reeves (larryr(AT)acm.org), May 25 2001