A072629 Parity of n*floor(log n).

0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 1

Author

Labos Elemer, Jun 28 2002

Keywords

• nonn

Comments

a(n)=1 for n: 3, 5, 7, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 149, 151, .... - Robert G. Wilson v, Feb 01 2015

Examples

			Parity either alternates or it is steadily 0. Intervals of such kind also change and return: 01010...0000....0101.., etc.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..100000
• Index entries for characteristic functions

Crossrefs

Cf. A004648, A072608, A072609, A072610, A072630.

Programs

Mathematica

f[n_] := Mod[n*Floor@ Log@ n, 2]; Array[f, 105] (* Robert G. Wilson v, Feb 01 2015 *)

PARI

a(n) = (log(n)\1*n)%2; \\ Charles R Greathouse IV, Sep 04 2015, corrected by Antti Karttunen, Feb 06 2019

Formula

a(n) = n*floor(log(n)) mod 2.