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A291256 Numbers n such that Sum_{k>=1} digits(k)/k = 1 where digits() are the digits of n in base 10, the least significant digit having index 1. 1
1, 20, 300, 2010, 4000, 50000, 100110, 102100, 200200, 300010, 302000, 400100, 600000, 7000000, 20001010, 20003000, 20101100, 20301000, 40000010, 40002000, 40100100, 40300000, 60001000, 80000000, 300000200, 300100010, 300102000, 300200100, 300400000, 320101000, 340100000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Michel Marcus and Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 59 terms from Michel Marcus)

EXAMPLE

20 is a term since 0/1 + 2/2 = 1.

2010 is a term since 0/1 + 1/2 + 0/3 + 2/4 = 1.

MATHEMATICA

ndig[n_] := Sort[Sum[e[[2]] 10^(1/e[[1]] - 1), {e, #}] & /@ Select[Tally /@ (Join[ {1/n}, #] & /@ IntegerPartitions[1 - 1/n, All, 1/Range[n]]), Max[Flatten[#]] < 10 &]]; Join @@ (ndig /@ Range[20]) (* Giovanni Resta, Aug 21 2017 *)

PROG

(PARI) isok(n) = my(d = Vecrev(digits(n))); sum(k=1, #d, d[k]/k) == 1;

CROSSREFS

Cf. A272036 (analog in base 2).

Sequence in context: A016255 A322052 A250014 * A250015 A138794 A077758

Adjacent sequences:  A291253 A291254 A291255 * A291257 A291258 A291259

KEYWORD

nonn,base

AUTHOR

Michel Marcus, Aug 21 2017

STATUS

approved

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Last modified May 26 04:46 EDT 2019. Contains 323579 sequences. (Running on oeis4.)