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Numbers in base -5.
11

%I #10 Apr 09 2016 17:06:25

%S 0,1,2,3,4,140,141,142,143,144,130,131,132,133,134,120,121,122,123,

%T 124,110,111,112,113,114,100,101,102,103,104,240,241,242,243,244,230,

%U 231,232,233,234,220,221,222,223,224,210,211,212,213,214,200,201,202,203

%N Numbers in base -5.

%D D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, 1969, Vol. 2, p. 189.

%H Chai Wah Wu, <a href="/A073786/b073786.txt">Table of n, a(n) for n = 0..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Negabinary.html">Negabinary</a>

%H Prepared and presented by Matthew Szudzik of Wolfram Research, <a href="http://library.wolfram.com/conferences/devconf99/challenge/">A Mathematica programming contest</a>

%t ToNegaBases[i_Integer, b_Integer] := FromDigits[ Rest[ Reverse[ Mod[ NestWhileList[(#1 - Mod[ #1, b])/-b &, i, #1 != 0 &], b]]]]; Table[ ToNegaBases[n, 5], {n, 0, 55}]

%o (Python)

%o def A073786(n):

%o s, q = '', n

%o while q >= 5 or q < 0:

%o q, r = divmod(q, -5)

%o if r < 0:

%o q += 1

%o r += 5

%o s += str(r)

%o return int(str(q)+s[::-1]) # _Chai Wah Wu_, Apr 09 2016

%Y Cf. A007091, A039724, A073785, A007608, A073787, A073788, A073789, A073790 & A039723.

%K base,easy,nonn

%O 0,3

%A _Robert G. Wilson v_, Aug 11 2002