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A004780 Binary expansion contains 2 adjacent 1's. 7
3, 6, 7, 11, 12, 13, 14, 15, 19, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 35, 38, 39, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 67, 70, 71, 75, 76, 77, 78, 79, 83, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of A003714. It appears that n is in the sequence if and only if C(3n,n) is even. - Benoit Cloitre, Mar 09 2003

Since the binary representation of these numbers contains two adjacent 1's, so for these values of n, we will have (n XOR 2n XOR 3n) != 0, and thus a two player Nim game with three heaps of (n, 2n, 3n) stones will be a winning configuration for the first player. - V. Raman, Sep 17 2012

A048728(a(n)) > 0. - Reinhard Zumkeller, May 13 2014

LINKS

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

Index entries for sequences related to binary expansion of n

FORMULA

a(n) ~ n. - Charles R Greathouse IV, Sep 19 2012

PROG

(PARI) is(n)=bitand(n, n+n)>0 \\ Charles R Greathouse IV, Sep 19 2012

(Haskell)

a004780 n = a004780_list !! (n-1)

a004780_list = filter ((> 1) . a048728) [1..]

-- Reinhard Zumkeller, May 13 2014

CROSSREFS

Cf. A005809, A048728, A242408.

Complement: A003714.

Subsequences (apart from any initial zero-term): A001196, A004755, A004767, A033428, A277335.

Sequence in context: A292608 A028754 A028795 * A292046 A051146 A136272

Adjacent sequences:  A004777 A004778 A004779 * A004781 A004782 A004783

KEYWORD

nonn,easy,base

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Offset corrected by Reinhard Zumkeller, Jul 28 2010

STATUS

approved

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Last modified February 24 19:45 EST 2018. Contains 299628 sequences. (Running on oeis4.)