%I #11 Apr 09 2016 17:08:25

%S 0,1,2,3,4,5,6,7,8,180,181,182,183,184,185,186,187,188,170,171,172,

%T 173,174,175,176,177,178,160,161,162,163,164,165,166,167,168,150,151,

%U 152,153,154,155,156,157,158,140,141,142,143,144,145,146,147,148,130,131

%N Numbers in base -9.

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

%H Chai Wah Wu, <a href="/A073790/b073790.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[(# - Mod[ #, b])/-b &, i, # != 0 &], b]; Table[ ToNegaBases[n, 9], {n, 0, 60}]

%o (Python)

%o def A073790(n):

%o s, q = '', n

%o while q >= 9 or q < 0:

%o q, r = divmod(q, -9)

%o if r < 0:

%o q += 1

%o r += 9

%o s += str(r)

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

%Y Cf. A007095, A039724, A073785, A007608, A073786, A073787, A073788, A073789 & A039723.

%K base,easy,nonn

%O 0,3

%A _Robert G. Wilson v_, Aug 11 2002