A375967 a(n) is the least number > n with the same digit average as n.

11, 13, 15, 17, 19, 39, 59, 79, 99, 1001, 20, 21, 22, 23, 24, 25, 26, 27, 28, 102, 30, 31, 32, 33, 34, 35, 36, 37, 38, 1005, 40, 41, 42, 43, 44, 45, 46, 47, 48, 105, 50, 51, 52, 53, 54, 55, 56, 57, 58, 1009, 60, 61, 62, 63, 64, 65, 66, 67, 68, 108, 70, 71, 72

Offset

1,1

Comments

The digit average of a number n is its sum of digits divided by its number of digits: A007953(n) / A055642(n).

Links

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, PARI program

Example

The first terms, alongside the corresponding digit average, are:
  n   a(n)  Digit average
  --  ----  -------------
   1    11              1
   2    13              2
   3    15              3
   4    17              4
   5    19              5
   6    39              6
   7    59              7
   8    79              8
   9    99              9
  10  1001            1/2
  11    20              1
  12    21            3/2

Mathematica

a[n_]:=Module[{k=0}, While[k<=n || Mean[IntegerDigits[k]] != Mean[IntegerDigits[n]], k++]; k]; Array[a, 63] (* Stefano Spezia, Sep 07 2024 *)

Prog

(PARI) avg(n, base) = my (d = digits(n, base)); vecsum(d) / max(1, #d)
a(n, base = 10) = { my (v = avg(n, base)); for (m = n+1, oo, if (avg(m, base)==v, return (m); ); ); }
(PARI) \\ See Links section.

Crossrefs

Cf. A007953, A055642, A228915, A375968.

Sequence in context: A152200 A277694 A179084 * A124569 A260826 A289699

Adjacent sequences: A375964 A375965 A375966 * A375968 A375969 A375970

Keyword

nonn,base,easy

Author

Rémy Sigrist, Sep 04 2024

Status

approved