

A212494


Base 2i representation of nonnegative integers.


5



0, 1, 2, 3, 10300, 10301, 10302, 10303, 10200, 10201, 10202, 10203, 10100, 10101, 10102, 10103, 10000, 10001, 10002, 10003, 20300, 20301, 20302, 20303, 20200, 20201, 20202, 20203, 20100, 20101, 20102, 20103
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OFFSET

0,3


COMMENTS

The use of negabinary dispenses with the need for sign bits and for keeping track of signed and unsigned data types. Similarly, the use of base 2i, or quaterimaginary, dispenses with the need to represent the real and imaginary parts of a complex number separately. (The term "quaterimaginary" appears in Knuth's landmark book on computer programming).
Quaterimaginary, based on the powers of 2i (twice the imaginary unit), uses the digits 0, 1, 2, 3. For purely real positive integers, the quaterimaginary representation is the same as negaquartal (base 4) except that 0's are "riffled" in, corresponding to the oddindexed powers of 2i which are purely imaginary numbers. Therefore, to obtain the base 2i representations of positive real numbers, the algorithm for base 4 representations can be employed with only a small adjustment.
To obtain the base 2i representation of a complex number a+bi, do as above for the real part, then again for the real part of 2i*(a+bi) = 2b+2ai, giving the digits corresponding to the oddindexed powers of 2i.
Omitting digits for odd powers of 2i (all 0's for the imaginary parts) (e.g. 20300 > 230) gives A007608 (nonnegative integers in base 4).


REFERENCES

Donald Knuth, The Art of Computer Programming. Volume 2, 2nd Edition. Reading, Massachussetts: AddisonWesley (1981): 189


LINKS

Joerg Arndt, Table of n, a(n) for n = 0..1000
Joerg Arndt, Radix 2i
Donald Knuth, An imaginary number system, Communications of the ACM 3 (4), April 1960, pp. 245247.
OEIS Wiki, Quaterimaginary base
Wikipedia, Quaterimaginary base


EXAMPLE

a(5) = 10301 because 5 = 1*(2i)^4+3*(2i)^2+1*(2i)^0 = 1*16+3*(4)+1*1


CROSSREFS

Cf. A212542 (Base 2i representation of negative integers).
Cf. A177505.
Cf. A007608 (Nonnegative integers in base 4).
Sequence in context: A137078 A146026 A115640 * A197635 A171161 A101445
Adjacent sequences: A212491 A212492 A212493 * A212495 A212496 A212497


KEYWORD

nonn,base


AUTHOR

Daniel Forgues, May 18 2012


STATUS

approved



