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A212526
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Negative integers in base -4.
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8
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13, 12, 11, 10, 23, 22, 21, 20, 33, 32, 31, 30, 1303, 1302, 1301, 1300, 1313, 1312, 1311, 1310, 1323, 1322, 1321, 1320, 1333, 1332, 1331, 1330, 1203, 1202, 1201, 1200, 1213, 1212, 1211, 1210, 1223, 1222, 1221, 1220
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Interleaving with zeros gives A212542 (base 2i representation of negative integers).
More precisely, a(n) is the representation of -n in base -4. - M. F. Hasler, May 21 2012
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LINKS
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EXAMPLE
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a(13)=1303: 1*(-4)^3 + 3*(-4)^2 + 0*(-4)^1 + 3*(-4)^0 = -64 + 48 +3 = -13.
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MAPLE
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a:= proc(n) local d, i, l, m;
m:= n;
l:= NULL;
for i from 0 while m>0 do
d:= irem(m, 4, 'm');
if irem (i, 2)=0 and d>0 then d:= 4-d; m:= m+1 fi;
l:= d, l
od; parse(cat(l))
end:
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PROG
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(PARI) A212526(n, s="")={n=-n; until(!n\=-4, s=Str(n%-4, s)); eval(s)} \\ M. F. Hasler, May 21 2012
(Python)
s, q = '', -n
while q >= 4 or q < 0:
q, r = divmod(q, -4)
if r < 0:
q += 1
r += 4
s += str(r)
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CROSSREFS
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Cf. A007608 (Nonnegative integers in base -4).
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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