A088742 -id:A088742 - cp's OEIS frontend

A091072 Positive numbers k such that the Kronecker Symbol (-1 / k) > 0.

1, 2, 4, 5, 8, 9, 10, 13, 16, 17, 18, 20, 21, 25, 26, 29, 32, 33, 34, 36, 37, 40, 41, 42, 45, 49, 50, 52, 53, 57, 58, 61, 64, 65, 66, 68, 69, 72, 73, 74, 77, 80, 81, 82, 84, 85, 89, 90, 93, 97, 98, 100, 101, 104, 105, 106, 109, 113, 114, 116, 117, 121, 122, 125, 128, 129

Offset: 1

Ralf Stephan, Feb 22 2004

Numbers whose odd part is of the form 4k+1. The bit to the left of the least significant bit of each term is unset. Either of form 2a(m) or 4k+1, k >= 0, 0 < m < n.
A000265(a(n)) is an element of A016813.
a(n) such that A038189(a(n)) = 0.
Numbers n such that kronecker(n, m) = kronecker(m, n) for all m. - Michael Somos, Sep 24 2005
The Dragon curve A014577 (but changing the offset to 1): (1, 1, 0, 1, 1, 0, 0, 1, 1, 1, ...) = the characteristic function of A091072. - Gary W. Adamson, Apr 11 2010
Also indices of 1 in A034947. - Jianing Song, Apr 24 2021
The terms in the sequence are the same as the terms in the odd columns of the table in A135764 with headings 4k+1: (1, 5, 9, 13...).  A014577(n) = 1 if n is in that set, but A014577(n) = 0 if n is in the set of even columns in the A135764 table. - Gary W. Adamson, May 29 2021
The asymptotic density of this sequence is 1/2. - Amiram Eldar, Sep 14 2024

			x + 2*x^2 + 4*x^3 + 5*x^4 + 8*x^5 + 9*x^6 + 10*x^7 + 13*x^8 + 16*x^9 + ...

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
J.-P. Allouche, G.-N. Han and J. Shallit, On some conjectures of P. Barry, arXiv:2006.08909 [math.NT], 2020.
Paul Barry, Some observations on the Rueppel sequence and associated Hankel determinants, arXiv:2005.04066 [math.CO], 2020.
Kevin Ryde, Iterations of the Dragon Curve, see index TurnLeft, with a(n) = TurnLeft(n-1).
J. E. S. Socolar and J. M. Taylor, An aperiodic hexagonal tile, arXiv:1003.4279 [math.CO], 2010.

Complement of A091067.

Cf. A000265, A014577 (characteristic function), A014707, A016813, A034947, A055975, A106841 (first of triplet), A088742 (first differences), A339597.

import Data.List (elemIndices)
a091072 n = a091072_list !! (n-1)
a091072_list = map (+ 1) $ elemIndices 0 a014707_list
-- Reinhard Zumkeller, Sep 28 2011

KS := (n, k) -> NumberTheory:-KroneckerSymbol(n, k):
aList := upto -> select(n -> 0 < KS(-1, n), [seq(1..upto)]):
aList(129);  # Peter Luschny, Mar 20 2025

Select[ Range[129], EvenQ[ (#/2^IntegerExponent[#, 2] - 1)/2 ] & ] (* Jean-François Alcover, Feb 16 2012, after Pari *)

for(n=1,200,if(((n/2^valuation(n,2)-1)/2)%2==0,print1(n",")))

{a(n) = local(m, c); if( n<1, 0, c=1; m=1; while( cMichael Somos, Sep 24 2005 */

a(n) = if(n=2*n-2, my(t=1); forstep(i=logint(n,2),0,-1, if(bittest(n,i)==t, n--;t=!t))); n+1; \\ Kevin Ryde, Mar 21 2021

isok(k) = kronecker(-1, k) > 0; \\ Michel Marcus, Mar 20 2025

A014707(a(n) + 1) = 0. - Reinhard Zumkeller, Sep 28 2011

A055975(a(n)) > 0. - Reinhard Zumkeller, Apr 28 2012

New name from Peter Luschny, Mar 20 2025

A106836 First differences of A060833 and (from a(2) onward) also of A091067 and A255068.

Original entry on oeis.org

3, 3, 1, 4, 1, 2, 1, 4, 3, 1, 1, 3, 1, 2, 1, 4, 3, 1, 4, 1, 2, 1, 1, 3, 3, 1, 1, 3, 1, 2, 1, 4, 3, 1, 4, 1, 2, 1, 4, 3, 1, 1, 3, 1, 2, 1, 1, 3, 3, 1, 4, 1, 2, 1, 1, 3, 3, 1, 1, 3, 1, 2, 1, 4, 3, 1, 4, 1, 2, 1, 4, 3, 1, 1, 3, 1, 2, 1, 4, 3, 1, 4, 1, 2, 1, 1, 3, 3, 1, 1, 3, 1, 2, 1, 1, 3, 3, 1, 4, 1, 2, 1

Offset: 1

Ralf Stephan, May 03 2005

nonn

From Antti Karttunen, Feb 20 2015: (Start)
Among the terms a(1) .. a(8192), 1 occurs 4095 times, 2 occurs 1024 times, 3 occurs 2048 times and 4 occurs 1025 times. No larger numbers can ever occur.
That these are the first differences of not just A091067 and A255068, but also of A060833 follows from N. Sato's Feb 12 2013 comment in the latter that "For n > 1, n is in the sequence (A060833) if and only if A038189(n-1) = 1."
Also length of runs in A236840 and A255070.
(End)

Antti Karttunen, Table of n, a(n) for n = 1..8192

Cf. A060833, A088742, A091067, A106837, A236840, A255058, A255068, A255070.

(define (A106836 n) (if (= 1 n) 3 (- (A091067 n) (A091067 (- n 1)))))

a(1) = 3, and for n > 1: a(n) = A091067(n) - A091067(n-1). - Antti Karttunen, Feb 20 2015

Name edited by Antti Karttunen, Feb 20 2015

cp's OEIS Frontend

A091072 Positive numbers k such that the Kronecker Symbol (-1 / k) > 0.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Haskell

Maple

Mathematica

PARI

PARI

PARI

PARI

Formula

Extensions

A106836 First differences of A060833 and (from a(2) onward) also of A091067 and A255068.

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Scheme

Formula

Extensions