A061955 - OEIS

A061955

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

142

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

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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