A061974 - OEIS

A061974

Numbers n such that n divides the (left) concatenation of all numbers <= n written in base 21 (most significant digit on right).

1, 5, 25, 125, 155, 160, 421, 1409, 729175, 2804576

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OFFSET

1,2

COMMENTS

This sequence differs from A029538 in that all least significant zeros are kept during concatenation.

No more terms < 7*10^6. - Lars Blomberg, Jul 27 2011

LINKS

Table of n, a(n) for n=1..10.

Index entries for related sequences

EXAMPLE

See A061955 for example.

MATHEMATICA

b = 21; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[Reverse[IntegerDigits[#, b]], c], b], #] &] (* Robert Price, Mar 09 2020 *)

PROG

(PARI) lista(nn, m=21) = my(c, t); for(k=1, nn, t+=m^c*fromdigits(Vecrev(digits(k, m)), m); c+=logint(m*k, m); if(t%k==0, print1(k, ", "))); \\ Jinyuan Wang, Dec 05 2020

CROSSREFS

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

Sequence in context: A036151 A271380 A036149 * A015950 A337950 A366323

Adjacent sequences: A061971 A061972 A061973 * A061975 A061976 A061977

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

a(9)-a(10) from Lars Blomberg, Jul 27 2011

STATUS

approved