A066322 -id:A066322 - cp's OEIS frontend

A066321 Binary representation of base-(i-1) expansion of n: replace i-1 with 2 in base-(i-1) expansion of n.

0, 1, 12, 13, 464, 465, 476, 477, 448, 449, 460, 461, 272, 273, 284, 285, 256, 257, 268, 269, 3280, 3281, 3292, 3293, 3264, 3265, 3276, 3277, 3088, 3089, 3100, 3101, 3072, 3073, 3084, 3085, 3536, 3537, 3548, 3549, 3520, 3521, 3532, 3533, 3344, 3345, 3356

Offset: 0

Marc LeBrun, Dec 14 2001

Here i = sqrt(-1).
First differences follow a strange period-16 pattern: 1 11 1 XXX 1 11 1 -29 1 11 1 -189 1 11 1 -29 where XXX is given by A066322. Number of one-bits is A066323.
From Andrey Zabolotskiy, Feb 06 2017: (Start)
(Observations.)
Actually, the sequence of the first differences can be split into blocks of size of any power of 2, and there will be only one position in the block that does not repeat. In this sense, one may say that the first differences follow (almost-)period-2^s pattern for any s > 0.
Specifically, the first differences are given by the formula: a(n+1)-a(n) = A282137(A007814((n xor ...110011001100) + 1)). Here binary representation of n is bitwise-xored with the period-4 bit sequence (A021913 written right-to-left) which is infinite or simply long enough; A007814(m) does not depend on the bits of m other than the least significant 1.
A282137 gives all first differences in the order of decreasing occurrence frequency.
(End)
Penney shows that since (i-1)^4 = -4, the representation a(n) of a real integer n is found by writing n in base -4 using digits 0 to 3 (A007608), changing those digits to bit strings 0000, 0001, 1100, 1101 respectively, and interpreting as binary. - Kevin Ryde, Sep 07 2019

			a(4) = 464 = 2^8 + 2^7 + 2^6 + 2^4 since (i-1)^8 + (i-1)^7 + (i-1)^6 + (i-1)^4 = 4.

D. E. Knuth, The Art of Computer Programming. Addison-Wesley, Reading, MA, 1969, Vol. 2, p. 172. (See also exercise 16, p. 177; answer, p. 494.)

Paul Tek, Table of n, a(n) for n = 0..10000
Joerg Arndt, The fxt demos: bit wizardry, radix(-1+i), C++ radix-m1pi.h function bin_real_to_radm1pi().
Solomon I. Khmelnik, Specialized Digital Computer for Operations with Complex Numbers, Questions of Radio Electronics, 12 (1964), 60-82 [in Russian].
W. J. Penney, A "binary" system for complex numbers, JACM 12 (1965), 247-248.
N. J. A. Sloane, Table of n, (I-1)^n for n = 0..100
Paul Tek, Perl program for this sequence
Andrey Zabolotskiy, negation & addition of Gaussian integers written in base i-1 [Python script].

Cf. A066322, A066323, A282137.
See A271472 for the conversion of these decimal numbers to binary.
See A009116 and A009545 for real and imaginary parts of (i-1)^n (except for signs).
See A256441 for expansions of -n.

f:= proc(n) option remember; local t,m;
   t:= n mod 4;
   procname(t) + 16*procname((t-n)/4)
end proc:
f(0):= 0: f(1):= 1: f(2):= 12: f(3):= 13:
seq(f(i),i=0..100); # Robert Israel, Oct 21 2016

a(n) = my(ret=0,p=0); while(n, ret+=[0,1,12,13][n%4+1]<Kevin Ryde, Sep 07 2019

Perl
```
See Links section.
```

from gmpy2 import c_divmod
u = ('0000','1000','0011','1011')
def A066321(n):
    if n == 0:
        return 0
    else:
        s, q = '', n
        while q:
            q, r = c_divmod(q, -4)
            s += u[r]
        return int(s[::-1],2) # Chai Wah Wu, Apr 09 2016

In "rebase notation" a(n) = (i-1)[n]2.

G.f. g(z) satisfies g(z) = z*(1+12*z+13*z^2)/(1-z^4) + 16*z^4*(13+12*z^4+z^8)/((1-z)*(1+z^4)*(1+z^8)) + 256*(1-z^16)*g(z^16)/(z^12-z^13). - Robert Israel, Oct 21 2016

A282137 Expansion of (24x^2-10x-1)/(16x^3-16x^2+x-1).

Original entry on oeis.org

1, 11, -29, -189, 451, 3011, -7229, -48189, 115651, 771011, -1850429, -12336189, 29606851, 197379011, -473709629, -3158064189, 7579354051, 50529027011, -121269664829, -808464432189, 1940314637251, 12935430915011, -31045034196029, -206966894640189

Offset: 0

Andrey Zabolotskiy, Feb 06 2017

Related to base i-1 representation of integers (Khmelnik encoding): presumably a(0) is the most common first difference of A066321 (occurs with density 1/2), a(1) is the second most common difference (density 1/4), a(2) has density 1/8, and so on; in particular, A066322 consists entirely of the terms a(n) with n>3.

Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,-16,16).

Cf. A066321, A066322, A218723.

LinearRecurrence[{0,0,0,257,0,0,0,-256}, {1, 11, -29, -189, 451, 3011, -7229, -48189}, 24]
LinearRecurrence[{1, -16, 16}, {1, 11, -29}, 24]

Vec((1 - 2*x)*(1 + 12*x) / ((1 - x)*(1 + 16*x^2)) + O(x^30)) \\ Colin Barker, Feb 07 2017

print([[1, 11, -29, -189][n%4] + [450, 3000, -7200, -48000][n%4]*(256**(n//4)-1)//255 for n in range(24)])

a(k+8) - 257 * a(k+4) + 256 * a(k) = 0, for k >= 0. - Altug Alkan, Feb 07 2017
G.f.: (24*x^2-10*x-1)/(16*x^3-16*x^2+x-1).
From Colin Barker, Feb 07 2017: (Start)
a(n) = (-13 + (15+25*i)*(-4*i)^n + (15-25*i)*(4*i)^n) / 17 where i=sqrt(-1).
a(n) = a(n-1) - 16*a(n-2) + 16*a(n-3) for n>2.
(End)

cp's OEIS Frontend

A066321 Binary representation of base-(i-1) expansion of n: replace i-1 with 2 in base-(i-1) expansion of n.

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