A061955 Numbers n such that n divides the (left) concatenation of all numbers <= n written in base 2 (most significant digit on right).

1, 3, 7, 29, 375, 545, 971, 1643, 37801, 435805, 554423, 565947, 645915, 733533, 871927, 9703985

Offset

1,2

Comments

This sequence differs from A029519 in that all least significant zeros are kept during concatenation.

No more terms < 10^7. - Lars Blomberg, Aug 31 2011

Links

Table of n, a(n) for n=1..16.

Index entries for related sequences

Example

7654321 -> (111)(011)(101)(001)(11)(01)(1) base 2 ->11101110100111011 base 2 = 122171 and 7 divides 122171.

Mathematica

b = 2; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[Reverse[IntegerDigits[#, b]], c], b], #] &] (* Robert Price, Mar 07 2020 *)

Prog

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

Crossrefs

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

Sequence in context: A082096 A119325 A048722 * A113834 A057181 A333393

Adjacent sequences: A061952 A061953 A061954 * A061956 A061957 A061958

Keyword

nonn,base,more

Author

Larry Reeves (larryr(AT)acm.org), May 24 2001

Extensions

Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002; Aug 25 2002

a(13)-a(16) from Lars Blomberg, Aug 31 2011

Status

approved