login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A212526 Negative integers in base -4. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Joerg Arndt, Table of n, a(n) for n = 1..1000

EXAMPLE

a(13)=1303:  1*(-4)^3 + 3*(-4)^2 + 0*(-4)^1 + 3*(-4)^0 = -64 + 48 +3 = -13.

MAPLE

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:

seq(a(n), n=1..60);  # Alois P. Heinz, May 20 2012

PROG

(PARI) A212526(n, s="")={n=-n; until(!n\=-4, s=Str(n%-4, s)); eval(s)}  \\ M. F. Hasler, May 21 2012

(Python)

def A212526(n):

    s, q = '', -n

    while q >= 4 or q < 0:

        q, r = divmod(q, -4)

        if r < 0:

            q += 1

            r += 4

        s += str(r)

    return int(str(q)+s[::-1]) # Chai Wah Wu, Apr 10 2016

CROSSREFS

Cf. A007608 (Nonnegative integers in base -4).

Sequence in context: A022969 A023455 A055124 * A019331 A004454 A113548

Adjacent sequences:  A212523 A212524 A212525 * A212527 A212528 A212529

KEYWORD

nonn,base

AUTHOR

Joerg Arndt, May 20 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 18 17:56 EST 2017. Contains 294894 sequences.