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A131851 Real part of the function z(n)=Sum(d(k)*i^k: d as in n=Sum(d(k)*2^k), i=sqrt(-1)). 12
0, 1, 0, 1, -1, 0, -1, 0, 0, 1, 0, 1, -1, 0, -1, 0, 1, 2, 1, 2, 0, 1, 0, 1, 1, 2, 1, 2, 0, 1, 0, 1, 0, 1, 0, 1, -1, 0, -1, 0, 0, 1, 0, 1, -1, 0, -1, 0, 1, 2, 1, 2, 0, 1, 0, 1, 1, 2, 1, 2, 0, 1, 0, 1, -1, 0, -1, 0, -2, -1, -2, -1, -1, 0, -1, 0, -2, -1, -2, -1, 0, 1, 0, 1, -1, 0, -1, 0, 0, 1, 0, 1, -1, 0, -1, 0, -1, 0, -1, 0, -2, -1, -2, -1, -1, 0, -1, 0, -2, -1, -2 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,18

COMMENTS

A131852(n) = Im(z(n));

z(A000079(n))=(A056594(n),A056594(n+3)); a(A000079(n))=A056594(n);

a(A131854(n))=0; a(A131861(n))>0; a(A131859(n))=1; a(A131863(n))<0;

z(A131853(n))=(0,0); z(A131856(n))=(0,1); z(A131858(n))=(1,0); z(A131860(n))=(1,1);

for n>0: a(A131865(n))=n and ABS(a(m))<n for m < A131865(n).

LINKS

R. Zumkeller, Table of n, a(n) for n = 0..10000

FORMULA

z(n) = if n=0 then (0, 0) else z(floor(n/2))*(0, 1) + (n mod 2, 0), complex multiplication.

MATHEMATICA

z[0] = 0; z[n_] := z[n] = z[Floor[n/2]]*I + Mod[n, 2]; Table[z[n] // Re, {n, 0, 110}] (* Jean-Fran├žois Alcover, Jul 03 2013 *)

CROSSREFS

Cf. A007088.

Sequence in context: A277899 A283760 A070088 * A104886 A215604 A139351

Adjacent sequences:  A131848 A131849 A131850 * A131852 A131853 A131854

KEYWORD

sign

AUTHOR

Reinhard Zumkeller, Jul 22 2007

STATUS

approved

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Last modified March 2 06:08 EST 2021. Contains 341742 sequences. (Running on oeis4.)