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, 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

Offset: 1

Author

Michel Marcus, Aug 21 2017

Keywords

• nonn
• base

Examples

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

Links

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

Crossrefs

Cf. A272036 (analog in base 2).

Programs

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 *)

PARI

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