login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A091072 Numbers a(n) such that odd part of a(n) is of form 4k+1. The bit to the left of least significant bit of a(n) is unset. 19
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

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

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

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

J. E. S. Socolar and J. M. Taylor, An aperiodic hexagonal tile, arXiv:1003.4279 [math.CO], 2010.

EXAMPLE

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 + ...

MATHEMATICA

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

PROG

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

(PARI) {a(n) = local(m, c); if( n<1, 0, c=1; m=1; while( c<n, m++; if( ((m / 2^valuation( m, 2) - 1) / 2)%2==0, c++)); m)} /* Michael Somos, Sep 24 2005 */

(Haskell)

import Data.List (elemIndices)

a091072 n = a091072_list !! (n-1)

a091072_list = map (+ 1) $ elemIndices 0 a014707_list

-- Reinhard Zumkeller, Sep 28 2011

CROSSREFS

Complement of A091067.

First differences are in A088742.

Cf. A014577. - Gary W. Adamson, Apr 11 2010

Sequence in context: A084581 A121996 A269176 * A001481 A248151 A245226

Adjacent sequences:  A091069 A091070 A091071 * A091073 A091074 A091075

KEYWORD

nonn,easy

AUTHOR

Ralf Stephan, Feb 22 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 21 21:27 EDT 2017. Contains 290908 sequences.