A165090 a(n) is the image of n under the base-8 Kaprekar map n -> (n with digits sorted into descending order) - (n with digits sorted into ascending order)

0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 7, 14, 21, 28, 35, 42, 14, 7, 0, 7, 14, 21, 28, 35, 21, 14, 7, 0, 7, 14, 21, 28, 28, 21, 14, 7, 0, 7, 14, 21, 35, 28, 21, 14, 7, 0, 7, 14, 42, 35, 28, 21, 14, 7, 0, 7, 49, 42, 35, 28, 21, 14, 7, 0, 63, 63, 126, 189, 252, 315, 378, 441, 63, 0, 63, 126, 189

Offset

0,9

Links

Indranil Ghosh, Table of n, a(n) for n = 0..32768 (terms 0..4096 from Joseph Myers)

Index entries for the Kaprekar map

Example

For n = 11, 11_10 = 13_8. So, a(11) = 31_8 - 13_8 = 25 - 11 = 14. - Indranil Ghosh, Feb 02 2017

Mathematica

a[n_] := With[{dd = IntegerDigits[n, 8]}, FromDigits[ReverseSort[dd], 8] - FromDigits[Sort[dd], 8]];
a /@ Range[0, 100] (* Jean-François Alcover, Jan 08 2020 *)

Prog

(Python)
def A165090(n):
    if n==0:return 0
    return int("".join(sorted(oct(n)[2:], reverse=True)), 8)-int("".join(sorted(oct(n)[2:])), 8) # Indranil Ghosh, Feb 02 2017

Crossrefs

Cf. A165091.

In other bases: A164884 (base 2), A164993 (base 3), A165012 (base 4), A165032 (base 5), A165051 (base 6), A165071 (base 7), A165110 (base 9), A151949 (base 10).

Sequence in context: A096444 A246918 A055957 * A341484 A117013 A176015

Adjacent sequences: A165087 A165088 A165089 * A165091 A165092 A165093

Keyword

base,nonn

Author

Joseph Myers, Sep 04 2009

Status

approved